forked from OSchip/llvm-project
2617 lines
99 KiB
C++
2617 lines
99 KiB
C++
//===- Reassociate.cpp - Reassociate binary expressions -------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass reassociates commutative expressions in an order that is designed
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// to promote better constant propagation, GCSE, LICM, PRE, etc.
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//
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// For example: 4 + (x + 5) -> x + (4 + 5)
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//
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// In the implementation of this algorithm, constants are assigned rank = 0,
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// function arguments are rank = 1, and other values are assigned ranks
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// corresponding to the reverse post order traversal of current function
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// (starting at 2), which effectively gives values in deep loops higher rank
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// than values not in loops.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar/Reassociate.h"
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#include "llvm/ADT/APFloat.h"
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#include "llvm/ADT/APInt.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/BasicAliasAnalysis.h"
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#include "llvm/Analysis/GlobalsModRef.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/Argument.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Constant.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/InstrTypes.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Operator.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/IR/Type.h"
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#include "llvm/IR/User.h"
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#include "llvm/IR/Value.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include <algorithm>
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#include <cassert>
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#include <utility>
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using namespace llvm;
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using namespace reassociate;
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using namespace PatternMatch;
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#define DEBUG_TYPE "reassociate"
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STATISTIC(NumChanged, "Number of insts reassociated");
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STATISTIC(NumAnnihil, "Number of expr tree annihilated");
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STATISTIC(NumFactor , "Number of multiplies factored");
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#ifndef NDEBUG
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/// Print out the expression identified in the Ops list.
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static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
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Module *M = I->getModule();
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dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
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<< *Ops[0].Op->getType() << '\t';
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for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
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dbgs() << "[ ";
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Ops[i].Op->printAsOperand(dbgs(), false, M);
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dbgs() << ", #" << Ops[i].Rank << "] ";
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}
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}
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#endif
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/// Utility class representing a non-constant Xor-operand. We classify
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/// non-constant Xor-Operands into two categories:
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/// C1) The operand is in the form "X & C", where C is a constant and C != ~0
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/// C2)
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/// C2.1) The operand is in the form of "X | C", where C is a non-zero
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/// constant.
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/// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
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/// operand as "E | 0"
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class llvm::reassociate::XorOpnd {
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public:
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XorOpnd(Value *V);
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bool isInvalid() const { return SymbolicPart == nullptr; }
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bool isOrExpr() const { return isOr; }
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Value *getValue() const { return OrigVal; }
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Value *getSymbolicPart() const { return SymbolicPart; }
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unsigned getSymbolicRank() const { return SymbolicRank; }
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const APInt &getConstPart() const { return ConstPart; }
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void Invalidate() { SymbolicPart = OrigVal = nullptr; }
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void setSymbolicRank(unsigned R) { SymbolicRank = R; }
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private:
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Value *OrigVal;
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Value *SymbolicPart;
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APInt ConstPart;
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unsigned SymbolicRank;
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bool isOr;
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};
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XorOpnd::XorOpnd(Value *V) {
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assert(!isa<ConstantInt>(V) && "No ConstantInt");
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OrigVal = V;
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Instruction *I = dyn_cast<Instruction>(V);
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SymbolicRank = 0;
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if (I && (I->getOpcode() == Instruction::Or ||
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I->getOpcode() == Instruction::And)) {
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Value *V0 = I->getOperand(0);
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Value *V1 = I->getOperand(1);
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const APInt *C;
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if (match(V0, m_APInt(C)))
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std::swap(V0, V1);
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if (match(V1, m_APInt(C))) {
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ConstPart = *C;
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SymbolicPart = V0;
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isOr = (I->getOpcode() == Instruction::Or);
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return;
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}
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}
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// view the operand as "V | 0"
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SymbolicPart = V;
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ConstPart = APInt::getNullValue(V->getType()->getScalarSizeInBits());
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isOr = true;
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}
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/// Return true if V is an instruction of the specified opcode and if it
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/// only has one use.
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static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
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auto *I = dyn_cast<Instruction>(V);
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if (I && I->hasOneUse() && I->getOpcode() == Opcode)
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if (!isa<FPMathOperator>(I) || I->isFast())
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return cast<BinaryOperator>(I);
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return nullptr;
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}
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static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
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unsigned Opcode2) {
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auto *I = dyn_cast<Instruction>(V);
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if (I && I->hasOneUse() &&
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(I->getOpcode() == Opcode1 || I->getOpcode() == Opcode2))
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if (!isa<FPMathOperator>(I) || I->isFast())
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return cast<BinaryOperator>(I);
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return nullptr;
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}
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void ReassociatePass::BuildRankMap(Function &F,
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ReversePostOrderTraversal<Function*> &RPOT) {
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unsigned Rank = 2;
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// Assign distinct ranks to function arguments.
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for (auto &Arg : F.args()) {
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ValueRankMap[&Arg] = ++Rank;
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LLVM_DEBUG(dbgs() << "Calculated Rank[" << Arg.getName() << "] = " << Rank
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<< "\n");
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}
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// Traverse basic blocks in ReversePostOrder.
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for (BasicBlock *BB : RPOT) {
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unsigned BBRank = RankMap[BB] = ++Rank << 16;
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// Walk the basic block, adding precomputed ranks for any instructions that
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// we cannot move. This ensures that the ranks for these instructions are
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// all different in the block.
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for (Instruction &I : *BB)
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if (mayBeMemoryDependent(I))
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ValueRankMap[&I] = ++BBRank;
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}
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}
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unsigned ReassociatePass::getRank(Value *V) {
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I) {
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if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
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return 0; // Otherwise it's a global or constant, rank 0.
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}
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if (unsigned Rank = ValueRankMap[I])
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return Rank; // Rank already known?
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// If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
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// we can reassociate expressions for code motion! Since we do not recurse
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// for PHI nodes, we cannot have infinite recursion here, because there
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// cannot be loops in the value graph that do not go through PHI nodes.
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unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
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for (unsigned i = 0, e = I->getNumOperands(); i != e && Rank != MaxRank; ++i)
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Rank = std::max(Rank, getRank(I->getOperand(i)));
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// If this is a 'not' or 'neg' instruction, do not count it for rank. This
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// assures us that X and ~X will have the same rank.
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if (!match(I, m_Not(m_Value())) && !match(I, m_Neg(m_Value())) &&
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!match(I, m_FNeg(m_Value())))
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++Rank;
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LLVM_DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank
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<< "\n");
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return ValueRankMap[I] = Rank;
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}
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// Canonicalize constants to RHS. Otherwise, sort the operands by rank.
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void ReassociatePass::canonicalizeOperands(Instruction *I) {
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assert(isa<BinaryOperator>(I) && "Expected binary operator.");
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assert(I->isCommutative() && "Expected commutative operator.");
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Value *LHS = I->getOperand(0);
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Value *RHS = I->getOperand(1);
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if (LHS == RHS || isa<Constant>(RHS))
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return;
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if (isa<Constant>(LHS) || getRank(RHS) < getRank(LHS))
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cast<BinaryOperator>(I)->swapOperands();
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}
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static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
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Instruction *InsertBefore, Value *FlagsOp) {
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if (S1->getType()->isIntOrIntVectorTy())
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return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
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else {
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BinaryOperator *Res =
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BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
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Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
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return Res;
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}
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}
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static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
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Instruction *InsertBefore, Value *FlagsOp) {
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if (S1->getType()->isIntOrIntVectorTy())
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return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
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else {
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BinaryOperator *Res =
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BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
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Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
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return Res;
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}
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}
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static Instruction *CreateNeg(Value *S1, const Twine &Name,
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Instruction *InsertBefore, Value *FlagsOp) {
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if (S1->getType()->isIntOrIntVectorTy())
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return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
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if (auto *FMFSource = dyn_cast<Instruction>(FlagsOp))
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return UnaryOperator::CreateFNegFMF(S1, FMFSource, Name, InsertBefore);
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return UnaryOperator::CreateFNeg(S1, Name, InsertBefore);
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}
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/// Replace 0-X with X*-1.
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static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
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assert((isa<UnaryOperator>(Neg) || isa<BinaryOperator>(Neg)) &&
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"Expected a Negate!");
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// FIXME: It's not safe to lower a unary FNeg into a FMul by -1.0.
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unsigned OpNo = isa<BinaryOperator>(Neg) ? 1 : 0;
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Type *Ty = Neg->getType();
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Constant *NegOne = Ty->isIntOrIntVectorTy() ?
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ConstantInt::getAllOnesValue(Ty) : ConstantFP::get(Ty, -1.0);
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BinaryOperator *Res = CreateMul(Neg->getOperand(OpNo), NegOne, "", Neg, Neg);
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Neg->setOperand(OpNo, Constant::getNullValue(Ty)); // Drop use of op.
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Res->takeName(Neg);
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Neg->replaceAllUsesWith(Res);
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Res->setDebugLoc(Neg->getDebugLoc());
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return Res;
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}
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/// Returns k such that lambda(2^Bitwidth) = 2^k, where lambda is the Carmichael
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/// function. This means that x^(2^k) === 1 mod 2^Bitwidth for
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/// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
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/// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
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/// even x in Bitwidth-bit arithmetic.
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static unsigned CarmichaelShift(unsigned Bitwidth) {
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if (Bitwidth < 3)
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return Bitwidth - 1;
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return Bitwidth - 2;
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}
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/// Add the extra weight 'RHS' to the existing weight 'LHS',
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/// reducing the combined weight using any special properties of the operation.
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/// The existing weight LHS represents the computation X op X op ... op X where
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/// X occurs LHS times. The combined weight represents X op X op ... op X with
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/// X occurring LHS + RHS times. If op is "Xor" for example then the combined
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/// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
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/// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
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static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
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// If we were working with infinite precision arithmetic then the combined
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// weight would be LHS + RHS. But we are using finite precision arithmetic,
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// and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
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// for nilpotent operations and addition, but not for idempotent operations
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// and multiplication), so it is important to correctly reduce the combined
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// weight back into range if wrapping would be wrong.
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// If RHS is zero then the weight didn't change.
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if (RHS.isMinValue())
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return;
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// If LHS is zero then the combined weight is RHS.
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if (LHS.isMinValue()) {
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LHS = RHS;
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return;
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}
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// From this point on we know that neither LHS nor RHS is zero.
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if (Instruction::isIdempotent(Opcode)) {
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// Idempotent means X op X === X, so any non-zero weight is equivalent to a
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// weight of 1. Keeping weights at zero or one also means that wrapping is
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// not a problem.
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assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
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return; // Return a weight of 1.
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}
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if (Instruction::isNilpotent(Opcode)) {
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// Nilpotent means X op X === 0, so reduce weights modulo 2.
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assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
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LHS = 0; // 1 + 1 === 0 modulo 2.
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return;
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}
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if (Opcode == Instruction::Add || Opcode == Instruction::FAdd) {
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// TODO: Reduce the weight by exploiting nsw/nuw?
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LHS += RHS;
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return;
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}
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assert((Opcode == Instruction::Mul || Opcode == Instruction::FMul) &&
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"Unknown associative operation!");
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unsigned Bitwidth = LHS.getBitWidth();
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// If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
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// can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
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// bit number x, since either x is odd in which case x^CM = 1, or x is even in
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// which case both x^W and x^(W - CM) are zero. By subtracting off multiples
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// of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
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// which by a happy accident means that they can always be represented using
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// Bitwidth bits.
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// TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
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// the Carmichael number).
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if (Bitwidth > 3) {
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/// CM - The value of Carmichael's lambda function.
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APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
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// Any weight W >= Threshold can be replaced with W - CM.
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APInt Threshold = CM + Bitwidth;
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assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!");
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// For Bitwidth 4 or more the following sum does not overflow.
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LHS += RHS;
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while (LHS.uge(Threshold))
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LHS -= CM;
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} else {
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// To avoid problems with overflow do everything the same as above but using
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// a larger type.
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unsigned CM = 1U << CarmichaelShift(Bitwidth);
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unsigned Threshold = CM + Bitwidth;
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assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold &&
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"Weights not reduced!");
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unsigned Total = LHS.getZExtValue() + RHS.getZExtValue();
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while (Total >= Threshold)
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Total -= CM;
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LHS = Total;
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}
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}
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using RepeatedValue = std::pair<Value*, APInt>;
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/// Given an associative binary expression, return the leaf
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/// nodes in Ops along with their weights (how many times the leaf occurs). The
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/// original expression is the same as
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/// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
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/// op
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/// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
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/// op
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/// ...
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/// op
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/// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
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///
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/// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
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///
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/// This routine may modify the function, in which case it returns 'true'. The
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/// changes it makes may well be destructive, changing the value computed by 'I'
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/// to something completely different. Thus if the routine returns 'true' then
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/// you MUST either replace I with a new expression computed from the Ops array,
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/// or use RewriteExprTree to put the values back in.
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///
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/// A leaf node is either not a binary operation of the same kind as the root
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/// node 'I' (i.e. is not a binary operator at all, or is, but with a different
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/// opcode), or is the same kind of binary operator but has a use which either
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/// does not belong to the expression, or does belong to the expression but is
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/// a leaf node. Every leaf node has at least one use that is a non-leaf node
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/// of the expression, while for non-leaf nodes (except for the root 'I') every
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/// use is a non-leaf node of the expression.
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///
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/// For example:
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/// expression graph node names
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///
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/// + | I
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/// / \ |
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/// + + | A, B
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/// / \ / \ |
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/// * + * | C, D, E
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/// / \ / \ / \ |
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/// + * | F, G
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///
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/// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
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/// that order) (C, 1), (E, 1), (F, 2), (G, 2).
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///
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/// The expression is maximal: if some instruction is a binary operator of the
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/// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
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/// then the instruction also belongs to the expression, is not a leaf node of
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/// it, and its operands also belong to the expression (but may be leaf nodes).
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///
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/// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
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/// order to ensure that every non-root node in the expression has *exactly one*
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/// use by a non-leaf node of the expression. This destruction means that the
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/// caller MUST either replace 'I' with a new expression or use something like
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/// RewriteExprTree to put the values back in if the routine indicates that it
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/// made a change by returning 'true'.
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///
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/// In the above example either the right operand of A or the left operand of B
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/// will be replaced by undef. If it is B's operand then this gives:
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///
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/// + | I
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/// / \ |
|
|
/// + + | A, B - operand of B replaced with undef
|
|
/// / \ \ |
|
|
/// * + * | C, D, E
|
|
/// / \ / \ / \ |
|
|
/// + * | F, G
|
|
///
|
|
/// Note that such undef operands can only be reached by passing through 'I'.
|
|
/// For example, if you visit operands recursively starting from a leaf node
|
|
/// then you will never see such an undef operand unless you get back to 'I',
|
|
/// which requires passing through a phi node.
|
|
///
|
|
/// Note that this routine may also mutate binary operators of the wrong type
|
|
/// that have all uses inside the expression (i.e. only used by non-leaf nodes
|
|
/// of the expression) if it can turn them into binary operators of the right
|
|
/// type and thus make the expression bigger.
|
|
static bool LinearizeExprTree(Instruction *I,
|
|
SmallVectorImpl<RepeatedValue> &Ops) {
|
|
assert((isa<UnaryOperator>(I) || isa<BinaryOperator>(I)) &&
|
|
"Expected a UnaryOperator or BinaryOperator!");
|
|
LLVM_DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
|
|
unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits();
|
|
unsigned Opcode = I->getOpcode();
|
|
assert(I->isAssociative() && I->isCommutative() &&
|
|
"Expected an associative and commutative operation!");
|
|
|
|
// Visit all operands of the expression, keeping track of their weight (the
|
|
// number of paths from the expression root to the operand, or if you like
|
|
// the number of times that operand occurs in the linearized expression).
|
|
// For example, if I = X + A, where X = A + B, then I, X and B have weight 1
|
|
// while A has weight two.
|
|
|
|
// Worklist of non-leaf nodes (their operands are in the expression too) along
|
|
// with their weights, representing a certain number of paths to the operator.
|
|
// If an operator occurs in the worklist multiple times then we found multiple
|
|
// ways to get to it.
|
|
SmallVector<std::pair<Instruction*, APInt>, 8> Worklist; // (Op, Weight)
|
|
Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1)));
|
|
bool Changed = false;
|
|
|
|
// Leaves of the expression are values that either aren't the right kind of
|
|
// operation (eg: a constant, or a multiply in an add tree), or are, but have
|
|
// some uses that are not inside the expression. For example, in I = X + X,
|
|
// X = A + B, the value X has two uses (by I) that are in the expression. If
|
|
// X has any other uses, for example in a return instruction, then we consider
|
|
// X to be a leaf, and won't analyze it further. When we first visit a value,
|
|
// if it has more than one use then at first we conservatively consider it to
|
|
// be a leaf. Later, as the expression is explored, we may discover some more
|
|
// uses of the value from inside the expression. If all uses turn out to be
|
|
// from within the expression (and the value is a binary operator of the right
|
|
// kind) then the value is no longer considered to be a leaf, and its operands
|
|
// are explored.
|
|
|
|
// Leaves - Keeps track of the set of putative leaves as well as the number of
|
|
// paths to each leaf seen so far.
|
|
using LeafMap = DenseMap<Value *, APInt>;
|
|
LeafMap Leaves; // Leaf -> Total weight so far.
|
|
SmallVector<Value *, 8> LeafOrder; // Ensure deterministic leaf output order.
|
|
|
|
#ifndef NDEBUG
|
|
SmallPtrSet<Value *, 8> Visited; // For sanity checking the iteration scheme.
|
|
#endif
|
|
while (!Worklist.empty()) {
|
|
std::pair<Instruction*, APInt> P = Worklist.pop_back_val();
|
|
I = P.first; // We examine the operands of this binary operator.
|
|
|
|
for (unsigned OpIdx = 0; OpIdx < I->getNumOperands(); ++OpIdx) { // Visit operands.
|
|
Value *Op = I->getOperand(OpIdx);
|
|
APInt Weight = P.second; // Number of paths to this operand.
|
|
LLVM_DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n");
|
|
assert(!Op->use_empty() && "No uses, so how did we get to it?!");
|
|
|
|
// If this is a binary operation of the right kind with only one use then
|
|
// add its operands to the expression.
|
|
if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
|
|
assert(Visited.insert(Op).second && "Not first visit!");
|
|
LLVM_DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n");
|
|
Worklist.push_back(std::make_pair(BO, Weight));
|
|
continue;
|
|
}
|
|
|
|
// Appears to be a leaf. Is the operand already in the set of leaves?
|
|
LeafMap::iterator It = Leaves.find(Op);
|
|
if (It == Leaves.end()) {
|
|
// Not in the leaf map. Must be the first time we saw this operand.
|
|
assert(Visited.insert(Op).second && "Not first visit!");
|
|
if (!Op->hasOneUse()) {
|
|
// This value has uses not accounted for by the expression, so it is
|
|
// not safe to modify. Mark it as being a leaf.
|
|
LLVM_DEBUG(dbgs()
|
|
<< "ADD USES LEAF: " << *Op << " (" << Weight << ")\n");
|
|
LeafOrder.push_back(Op);
|
|
Leaves[Op] = Weight;
|
|
continue;
|
|
}
|
|
// No uses outside the expression, try morphing it.
|
|
} else {
|
|
// Already in the leaf map.
|
|
assert(It != Leaves.end() && Visited.count(Op) &&
|
|
"In leaf map but not visited!");
|
|
|
|
// Update the number of paths to the leaf.
|
|
IncorporateWeight(It->second, Weight, Opcode);
|
|
|
|
#if 0 // TODO: Re-enable once PR13021 is fixed.
|
|
// The leaf already has one use from inside the expression. As we want
|
|
// exactly one such use, drop this new use of the leaf.
|
|
assert(!Op->hasOneUse() && "Only one use, but we got here twice!");
|
|
I->setOperand(OpIdx, UndefValue::get(I->getType()));
|
|
Changed = true;
|
|
|
|
// If the leaf is a binary operation of the right kind and we now see
|
|
// that its multiple original uses were in fact all by nodes belonging
|
|
// to the expression, then no longer consider it to be a leaf and add
|
|
// its operands to the expression.
|
|
if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
|
|
LLVM_DEBUG(dbgs() << "UNLEAF: " << *Op << " (" << It->second << ")\n");
|
|
Worklist.push_back(std::make_pair(BO, It->second));
|
|
Leaves.erase(It);
|
|
continue;
|
|
}
|
|
#endif
|
|
|
|
// If we still have uses that are not accounted for by the expression
|
|
// then it is not safe to modify the value.
|
|
if (!Op->hasOneUse())
|
|
continue;
|
|
|
|
// No uses outside the expression, try morphing it.
|
|
Weight = It->second;
|
|
Leaves.erase(It); // Since the value may be morphed below.
|
|
}
|
|
|
|
// At this point we have a value which, first of all, is not a binary
|
|
// expression of the right kind, and secondly, is only used inside the
|
|
// expression. This means that it can safely be modified. See if we
|
|
// can usefully morph it into an expression of the right kind.
|
|
assert((!isa<Instruction>(Op) ||
|
|
cast<Instruction>(Op)->getOpcode() != Opcode
|
|
|| (isa<FPMathOperator>(Op) &&
|
|
!cast<Instruction>(Op)->isFast())) &&
|
|
"Should have been handled above!");
|
|
assert(Op->hasOneUse() && "Has uses outside the expression tree!");
|
|
|
|
// If this is a multiply expression, turn any internal negations into
|
|
// multiplies by -1 so they can be reassociated.
|
|
if (Instruction *Tmp = dyn_cast<Instruction>(Op))
|
|
if ((Opcode == Instruction::Mul && match(Tmp, m_Neg(m_Value()))) ||
|
|
(Opcode == Instruction::FMul && match(Tmp, m_FNeg(m_Value())))) {
|
|
LLVM_DEBUG(dbgs()
|
|
<< "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
|
|
Tmp = LowerNegateToMultiply(Tmp);
|
|
LLVM_DEBUG(dbgs() << *Tmp << '\n');
|
|
Worklist.push_back(std::make_pair(Tmp, Weight));
|
|
Changed = true;
|
|
continue;
|
|
}
|
|
|
|
// Failed to morph into an expression of the right type. This really is
|
|
// a leaf.
|
|
LLVM_DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n");
|
|
assert(!isReassociableOp(Op, Opcode) && "Value was morphed?");
|
|
LeafOrder.push_back(Op);
|
|
Leaves[Op] = Weight;
|
|
}
|
|
}
|
|
|
|
// The leaves, repeated according to their weights, represent the linearized
|
|
// form of the expression.
|
|
for (unsigned i = 0, e = LeafOrder.size(); i != e; ++i) {
|
|
Value *V = LeafOrder[i];
|
|
LeafMap::iterator It = Leaves.find(V);
|
|
if (It == Leaves.end())
|
|
// Node initially thought to be a leaf wasn't.
|
|
continue;
|
|
assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
|
|
APInt Weight = It->second;
|
|
if (Weight.isMinValue())
|
|
// Leaf already output or weight reduction eliminated it.
|
|
continue;
|
|
// Ensure the leaf is only output once.
|
|
It->second = 0;
|
|
Ops.push_back(std::make_pair(V, Weight));
|
|
}
|
|
|
|
// For nilpotent operations or addition there may be no operands, for example
|
|
// because the expression was "X xor X" or consisted of 2^Bitwidth additions:
|
|
// in both cases the weight reduces to 0 causing the value to be skipped.
|
|
if (Ops.empty()) {
|
|
Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
|
|
assert(Identity && "Associative operation without identity!");
|
|
Ops.emplace_back(Identity, APInt(Bitwidth, 1));
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
/// Now that the operands for this expression tree are
|
|
/// linearized and optimized, emit them in-order.
|
|
void ReassociatePass::RewriteExprTree(BinaryOperator *I,
|
|
SmallVectorImpl<ValueEntry> &Ops) {
|
|
assert(Ops.size() > 1 && "Single values should be used directly!");
|
|
|
|
// Since our optimizations should never increase the number of operations, the
|
|
// new expression can usually be written reusing the existing binary operators
|
|
// from the original expression tree, without creating any new instructions,
|
|
// though the rewritten expression may have a completely different topology.
|
|
// We take care to not change anything if the new expression will be the same
|
|
// as the original. If more than trivial changes (like commuting operands)
|
|
// were made then we are obliged to clear out any optional subclass data like
|
|
// nsw flags.
|
|
|
|
/// NodesToRewrite - Nodes from the original expression available for writing
|
|
/// the new expression into.
|
|
SmallVector<BinaryOperator*, 8> NodesToRewrite;
|
|
unsigned Opcode = I->getOpcode();
|
|
BinaryOperator *Op = I;
|
|
|
|
/// NotRewritable - The operands being written will be the leaves of the new
|
|
/// expression and must not be used as inner nodes (via NodesToRewrite) by
|
|
/// mistake. Inner nodes are always reassociable, and usually leaves are not
|
|
/// (if they were they would have been incorporated into the expression and so
|
|
/// would not be leaves), so most of the time there is no danger of this. But
|
|
/// in rare cases a leaf may become reassociable if an optimization kills uses
|
|
/// of it, or it may momentarily become reassociable during rewriting (below)
|
|
/// due it being removed as an operand of one of its uses. Ensure that misuse
|
|
/// of leaf nodes as inner nodes cannot occur by remembering all of the future
|
|
/// leaves and refusing to reuse any of them as inner nodes.
|
|
SmallPtrSet<Value*, 8> NotRewritable;
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
|
|
NotRewritable.insert(Ops[i].Op);
|
|
|
|
// ExpressionChanged - Non-null if the rewritten expression differs from the
|
|
// original in some non-trivial way, requiring the clearing of optional flags.
|
|
// Flags are cleared from the operator in ExpressionChanged up to I inclusive.
|
|
BinaryOperator *ExpressionChanged = nullptr;
|
|
for (unsigned i = 0; ; ++i) {
|
|
// The last operation (which comes earliest in the IR) is special as both
|
|
// operands will come from Ops, rather than just one with the other being
|
|
// a subexpression.
|
|
if (i+2 == Ops.size()) {
|
|
Value *NewLHS = Ops[i].Op;
|
|
Value *NewRHS = Ops[i+1].Op;
|
|
Value *OldLHS = Op->getOperand(0);
|
|
Value *OldRHS = Op->getOperand(1);
|
|
|
|
if (NewLHS == OldLHS && NewRHS == OldRHS)
|
|
// Nothing changed, leave it alone.
|
|
break;
|
|
|
|
if (NewLHS == OldRHS && NewRHS == OldLHS) {
|
|
// The order of the operands was reversed. Swap them.
|
|
LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
|
|
Op->swapOperands();
|
|
LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
|
|
MadeChange = true;
|
|
++NumChanged;
|
|
break;
|
|
}
|
|
|
|
// The new operation differs non-trivially from the original. Overwrite
|
|
// the old operands with the new ones.
|
|
LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
|
|
if (NewLHS != OldLHS) {
|
|
BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
|
|
if (BO && !NotRewritable.count(BO))
|
|
NodesToRewrite.push_back(BO);
|
|
Op->setOperand(0, NewLHS);
|
|
}
|
|
if (NewRHS != OldRHS) {
|
|
BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
|
|
if (BO && !NotRewritable.count(BO))
|
|
NodesToRewrite.push_back(BO);
|
|
Op->setOperand(1, NewRHS);
|
|
}
|
|
LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
|
|
|
|
ExpressionChanged = Op;
|
|
MadeChange = true;
|
|
++NumChanged;
|
|
|
|
break;
|
|
}
|
|
|
|
// Not the last operation. The left-hand side will be a sub-expression
|
|
// while the right-hand side will be the current element of Ops.
|
|
Value *NewRHS = Ops[i].Op;
|
|
if (NewRHS != Op->getOperand(1)) {
|
|
LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
|
|
if (NewRHS == Op->getOperand(0)) {
|
|
// The new right-hand side was already present as the left operand. If
|
|
// we are lucky then swapping the operands will sort out both of them.
|
|
Op->swapOperands();
|
|
} else {
|
|
// Overwrite with the new right-hand side.
|
|
BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
|
|
if (BO && !NotRewritable.count(BO))
|
|
NodesToRewrite.push_back(BO);
|
|
Op->setOperand(1, NewRHS);
|
|
ExpressionChanged = Op;
|
|
}
|
|
LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
|
|
MadeChange = true;
|
|
++NumChanged;
|
|
}
|
|
|
|
// Now deal with the left-hand side. If this is already an operation node
|
|
// from the original expression then just rewrite the rest of the expression
|
|
// into it.
|
|
BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
|
|
if (BO && !NotRewritable.count(BO)) {
|
|
Op = BO;
|
|
continue;
|
|
}
|
|
|
|
// Otherwise, grab a spare node from the original expression and use that as
|
|
// the left-hand side. If there are no nodes left then the optimizers made
|
|
// an expression with more nodes than the original! This usually means that
|
|
// they did something stupid but it might mean that the problem was just too
|
|
// hard (finding the mimimal number of multiplications needed to realize a
|
|
// multiplication expression is NP-complete). Whatever the reason, smart or
|
|
// stupid, create a new node if there are none left.
|
|
BinaryOperator *NewOp;
|
|
if (NodesToRewrite.empty()) {
|
|
Constant *Undef = UndefValue::get(I->getType());
|
|
NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
|
|
Undef, Undef, "", I);
|
|
if (NewOp->getType()->isFPOrFPVectorTy())
|
|
NewOp->setFastMathFlags(I->getFastMathFlags());
|
|
} else {
|
|
NewOp = NodesToRewrite.pop_back_val();
|
|
}
|
|
|
|
LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
|
|
Op->setOperand(0, NewOp);
|
|
LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
|
|
ExpressionChanged = Op;
|
|
MadeChange = true;
|
|
++NumChanged;
|
|
Op = NewOp;
|
|
}
|
|
|
|
// If the expression changed non-trivially then clear out all subclass data
|
|
// starting from the operator specified in ExpressionChanged, and compactify
|
|
// the operators to just before the expression root to guarantee that the
|
|
// expression tree is dominated by all of Ops.
|
|
if (ExpressionChanged)
|
|
do {
|
|
// Preserve FastMathFlags.
|
|
if (isa<FPMathOperator>(I)) {
|
|
FastMathFlags Flags = I->getFastMathFlags();
|
|
ExpressionChanged->clearSubclassOptionalData();
|
|
ExpressionChanged->setFastMathFlags(Flags);
|
|
} else
|
|
ExpressionChanged->clearSubclassOptionalData();
|
|
|
|
if (ExpressionChanged == I)
|
|
break;
|
|
|
|
// Discard any debug info related to the expressions that has changed (we
|
|
// can leave debug infor related to the root, since the result of the
|
|
// expression tree should be the same even after reassociation).
|
|
replaceDbgUsesWithUndef(ExpressionChanged);
|
|
|
|
ExpressionChanged->moveBefore(I);
|
|
ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->user_begin());
|
|
} while (true);
|
|
|
|
// Throw away any left over nodes from the original expression.
|
|
for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
|
|
RedoInsts.insert(NodesToRewrite[i]);
|
|
}
|
|
|
|
/// Insert instructions before the instruction pointed to by BI,
|
|
/// that computes the negative version of the value specified. The negative
|
|
/// version of the value is returned, and BI is left pointing at the instruction
|
|
/// that should be processed next by the reassociation pass.
|
|
/// Also add intermediate instructions to the redo list that are modified while
|
|
/// pushing the negates through adds. These will be revisited to see if
|
|
/// additional opportunities have been exposed.
|
|
static Value *NegateValue(Value *V, Instruction *BI,
|
|
ReassociatePass::OrderedSet &ToRedo) {
|
|
if (auto *C = dyn_cast<Constant>(V))
|
|
return C->getType()->isFPOrFPVectorTy() ? ConstantExpr::getFNeg(C) :
|
|
ConstantExpr::getNeg(C);
|
|
|
|
// We are trying to expose opportunity for reassociation. One of the things
|
|
// that we want to do to achieve this is to push a negation as deep into an
|
|
// expression chain as possible, to expose the add instructions. In practice,
|
|
// this means that we turn this:
|
|
// X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
|
|
// so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
|
|
// the constants. We assume that instcombine will clean up the mess later if
|
|
// we introduce tons of unnecessary negation instructions.
|
|
//
|
|
if (BinaryOperator *I =
|
|
isReassociableOp(V, Instruction::Add, Instruction::FAdd)) {
|
|
// Push the negates through the add.
|
|
I->setOperand(0, NegateValue(I->getOperand(0), BI, ToRedo));
|
|
I->setOperand(1, NegateValue(I->getOperand(1), BI, ToRedo));
|
|
if (I->getOpcode() == Instruction::Add) {
|
|
I->setHasNoUnsignedWrap(false);
|
|
I->setHasNoSignedWrap(false);
|
|
}
|
|
|
|
// We must move the add instruction here, because the neg instructions do
|
|
// not dominate the old add instruction in general. By moving it, we are
|
|
// assured that the neg instructions we just inserted dominate the
|
|
// instruction we are about to insert after them.
|
|
//
|
|
I->moveBefore(BI);
|
|
I->setName(I->getName()+".neg");
|
|
|
|
// Add the intermediate negates to the redo list as processing them later
|
|
// could expose more reassociating opportunities.
|
|
ToRedo.insert(I);
|
|
return I;
|
|
}
|
|
|
|
// Okay, we need to materialize a negated version of V with an instruction.
|
|
// Scan the use lists of V to see if we have one already.
|
|
for (User *U : V->users()) {
|
|
if (!match(U, m_Neg(m_Value())) && !match(U, m_FNeg(m_Value())))
|
|
continue;
|
|
|
|
// We found one! Now we have to make sure that the definition dominates
|
|
// this use. We do this by moving it to the entry block (if it is a
|
|
// non-instruction value) or right after the definition. These negates will
|
|
// be zapped by reassociate later, so we don't need much finesse here.
|
|
Instruction *TheNeg = cast<Instruction>(U);
|
|
|
|
// Verify that the negate is in this function, V might be a constant expr.
|
|
if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
|
|
continue;
|
|
|
|
bool FoundCatchSwitch = false;
|
|
|
|
BasicBlock::iterator InsertPt;
|
|
if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
|
|
if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
|
|
InsertPt = II->getNormalDest()->begin();
|
|
} else {
|
|
InsertPt = ++InstInput->getIterator();
|
|
}
|
|
|
|
const BasicBlock *BB = InsertPt->getParent();
|
|
|
|
// Make sure we don't move anything before PHIs or exception
|
|
// handling pads.
|
|
while (InsertPt != BB->end() && (isa<PHINode>(InsertPt) ||
|
|
InsertPt->isEHPad())) {
|
|
if (isa<CatchSwitchInst>(InsertPt))
|
|
// A catchswitch cannot have anything in the block except
|
|
// itself and PHIs. We'll bail out below.
|
|
FoundCatchSwitch = true;
|
|
++InsertPt;
|
|
}
|
|
} else {
|
|
InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
|
|
}
|
|
|
|
// We found a catchswitch in the block where we want to move the
|
|
// neg. We cannot move anything into that block. Bail and just
|
|
// create the neg before BI, as if we hadn't found an existing
|
|
// neg.
|
|
if (FoundCatchSwitch)
|
|
break;
|
|
|
|
TheNeg->moveBefore(&*InsertPt);
|
|
if (TheNeg->getOpcode() == Instruction::Sub) {
|
|
TheNeg->setHasNoUnsignedWrap(false);
|
|
TheNeg->setHasNoSignedWrap(false);
|
|
} else {
|
|
TheNeg->andIRFlags(BI);
|
|
}
|
|
ToRedo.insert(TheNeg);
|
|
return TheNeg;
|
|
}
|
|
|
|
// Insert a 'neg' instruction that subtracts the value from zero to get the
|
|
// negation.
|
|
Instruction *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI);
|
|
ToRedo.insert(NewNeg);
|
|
return NewNeg;
|
|
}
|
|
|
|
// See if this `or` looks like an load widening reduction, i.e. that it
|
|
// consists of an `or`/`shl`/`zext`/`load` nodes only. Note that we don't
|
|
// ensure that the pattern is *really* a load widening reduction,
|
|
// we do not ensure that it can really be replaced with a widened load,
|
|
// only that it mostly looks like one.
|
|
static bool isLoadCombineCandidate(Instruction *Or) {
|
|
SmallVector<Instruction *, 8> Worklist;
|
|
SmallSet<Instruction *, 8> Visited;
|
|
|
|
auto Enqueue = [&](Value *V) {
|
|
auto *I = dyn_cast<Instruction>(V);
|
|
// Each node of an `or` reduction must be an instruction,
|
|
if (!I)
|
|
return false; // Node is certainly not part of an `or` load reduction.
|
|
// Only process instructions we have never processed before.
|
|
if (Visited.insert(I).second)
|
|
Worklist.emplace_back(I);
|
|
return true; // Will need to look at parent nodes.
|
|
};
|
|
|
|
if (!Enqueue(Or))
|
|
return false; // Not an `or` reduction pattern.
|
|
|
|
while (!Worklist.empty()) {
|
|
auto *I = Worklist.pop_back_val();
|
|
|
|
// Okay, which instruction is this node?
|
|
switch (I->getOpcode()) {
|
|
case Instruction::Or:
|
|
// Got an `or` node. That's fine, just recurse into it's operands.
|
|
for (Value *Op : I->operands())
|
|
if (!Enqueue(Op))
|
|
return false; // Not an `or` reduction pattern.
|
|
continue;
|
|
|
|
case Instruction::Shl:
|
|
case Instruction::ZExt:
|
|
// `shl`/`zext` nodes are fine, just recurse into their base operand.
|
|
if (!Enqueue(I->getOperand(0)))
|
|
return false; // Not an `or` reduction pattern.
|
|
continue;
|
|
|
|
case Instruction::Load:
|
|
// Perfect, `load` node means we've reached an edge of the graph.
|
|
continue;
|
|
|
|
default: // Unknown node.
|
|
return false; // Not an `or` reduction pattern.
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/// Return true if it may be profitable to convert this (X|Y) into (X+Y).
|
|
static bool shouldConvertOrWithNoCommonBitsToAdd(Instruction *Or) {
|
|
// Don't bother to convert this up unless either the LHS is an associable add
|
|
// or subtract or mul or if this is only used by one of the above.
|
|
// This is only a compile-time improvement, it is not needed for correctness!
|
|
auto isInteresting = [](Value *V) {
|
|
for (auto Op : {Instruction::Add, Instruction::Sub, Instruction::Mul,
|
|
Instruction::Shl})
|
|
if (isReassociableOp(V, Op))
|
|
return true;
|
|
return false;
|
|
};
|
|
|
|
if (any_of(Or->operands(), isInteresting))
|
|
return true;
|
|
|
|
Value *VB = Or->user_back();
|
|
if (Or->hasOneUse() && isInteresting(VB))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/// If we have (X|Y), and iff X and Y have no common bits set,
|
|
/// transform this into (X+Y) to allow arithmetics reassociation.
|
|
static BinaryOperator *convertOrWithNoCommonBitsToAdd(Instruction *Or) {
|
|
// Convert an or into an add.
|
|
BinaryOperator *New =
|
|
CreateAdd(Or->getOperand(0), Or->getOperand(1), "", Or, Or);
|
|
New->setHasNoSignedWrap();
|
|
New->setHasNoUnsignedWrap();
|
|
New->takeName(Or);
|
|
|
|
// Everyone now refers to the add instruction.
|
|
Or->replaceAllUsesWith(New);
|
|
New->setDebugLoc(Or->getDebugLoc());
|
|
|
|
LLVM_DEBUG(dbgs() << "Converted or into an add: " << *New << '\n');
|
|
return New;
|
|
}
|
|
|
|
/// Return true if we should break up this subtract of X-Y into (X + -Y).
|
|
static bool ShouldBreakUpSubtract(Instruction *Sub) {
|
|
// If this is a negation, we can't split it up!
|
|
if (match(Sub, m_Neg(m_Value())) || match(Sub, m_FNeg(m_Value())))
|
|
return false;
|
|
|
|
// Don't breakup X - undef.
|
|
if (isa<UndefValue>(Sub->getOperand(1)))
|
|
return false;
|
|
|
|
// Don't bother to break this up unless either the LHS is an associable add or
|
|
// subtract or if this is only used by one.
|
|
Value *V0 = Sub->getOperand(0);
|
|
if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) ||
|
|
isReassociableOp(V0, Instruction::Sub, Instruction::FSub))
|
|
return true;
|
|
Value *V1 = Sub->getOperand(1);
|
|
if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) ||
|
|
isReassociableOp(V1, Instruction::Sub, Instruction::FSub))
|
|
return true;
|
|
Value *VB = Sub->user_back();
|
|
if (Sub->hasOneUse() &&
|
|
(isReassociableOp(VB, Instruction::Add, Instruction::FAdd) ||
|
|
isReassociableOp(VB, Instruction::Sub, Instruction::FSub)))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/// If we have (X-Y), and if either X is an add, or if this is only used by an
|
|
/// add, transform this into (X+(0-Y)) to promote better reassociation.
|
|
static BinaryOperator *BreakUpSubtract(Instruction *Sub,
|
|
ReassociatePass::OrderedSet &ToRedo) {
|
|
// Convert a subtract into an add and a neg instruction. This allows sub
|
|
// instructions to be commuted with other add instructions.
|
|
//
|
|
// Calculate the negative value of Operand 1 of the sub instruction,
|
|
// and set it as the RHS of the add instruction we just made.
|
|
Value *NegVal = NegateValue(Sub->getOperand(1), Sub, ToRedo);
|
|
BinaryOperator *New = CreateAdd(Sub->getOperand(0), NegVal, "", Sub, Sub);
|
|
Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
|
|
Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
|
|
New->takeName(Sub);
|
|
|
|
// Everyone now refers to the add instruction.
|
|
Sub->replaceAllUsesWith(New);
|
|
New->setDebugLoc(Sub->getDebugLoc());
|
|
|
|
LLVM_DEBUG(dbgs() << "Negated: " << *New << '\n');
|
|
return New;
|
|
}
|
|
|
|
/// If this is a shift of a reassociable multiply or is used by one, change
|
|
/// this into a multiply by a constant to assist with further reassociation.
|
|
static BinaryOperator *ConvertShiftToMul(Instruction *Shl) {
|
|
Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
|
|
auto *SA = cast<ConstantInt>(Shl->getOperand(1));
|
|
MulCst = ConstantExpr::getShl(MulCst, SA);
|
|
|
|
BinaryOperator *Mul =
|
|
BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
|
|
Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op.
|
|
Mul->takeName(Shl);
|
|
|
|
// Everyone now refers to the mul instruction.
|
|
Shl->replaceAllUsesWith(Mul);
|
|
Mul->setDebugLoc(Shl->getDebugLoc());
|
|
|
|
// We can safely preserve the nuw flag in all cases. It's also safe to turn a
|
|
// nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
|
|
// handling. It can be preserved as long as we're not left shifting by
|
|
// bitwidth - 1.
|
|
bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
|
|
bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
|
|
unsigned BitWidth = Shl->getType()->getIntegerBitWidth();
|
|
if (NSW && (NUW || SA->getValue().ult(BitWidth - 1)))
|
|
Mul->setHasNoSignedWrap(true);
|
|
Mul->setHasNoUnsignedWrap(NUW);
|
|
return Mul;
|
|
}
|
|
|
|
/// Scan backwards and forwards among values with the same rank as element i
|
|
/// to see if X exists. If X does not exist, return i. This is useful when
|
|
/// scanning for 'x' when we see '-x' because they both get the same rank.
|
|
static unsigned FindInOperandList(const SmallVectorImpl<ValueEntry> &Ops,
|
|
unsigned i, Value *X) {
|
|
unsigned XRank = Ops[i].Rank;
|
|
unsigned e = Ops.size();
|
|
for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
|
|
if (Ops[j].Op == X)
|
|
return j;
|
|
if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
|
|
if (Instruction *I2 = dyn_cast<Instruction>(X))
|
|
if (I1->isIdenticalTo(I2))
|
|
return j;
|
|
}
|
|
// Scan backwards.
|
|
for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
|
|
if (Ops[j].Op == X)
|
|
return j;
|
|
if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
|
|
if (Instruction *I2 = dyn_cast<Instruction>(X))
|
|
if (I1->isIdenticalTo(I2))
|
|
return j;
|
|
}
|
|
return i;
|
|
}
|
|
|
|
/// Emit a tree of add instructions, summing Ops together
|
|
/// and returning the result. Insert the tree before I.
|
|
static Value *EmitAddTreeOfValues(Instruction *I,
|
|
SmallVectorImpl<WeakTrackingVH> &Ops) {
|
|
if (Ops.size() == 1) return Ops.back();
|
|
|
|
Value *V1 = Ops.pop_back_val();
|
|
Value *V2 = EmitAddTreeOfValues(I, Ops);
|
|
return CreateAdd(V2, V1, "reass.add", I, I);
|
|
}
|
|
|
|
/// If V is an expression tree that is a multiplication sequence,
|
|
/// and if this sequence contains a multiply by Factor,
|
|
/// remove Factor from the tree and return the new tree.
|
|
Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor) {
|
|
BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
|
|
if (!BO)
|
|
return nullptr;
|
|
|
|
SmallVector<RepeatedValue, 8> Tree;
|
|
MadeChange |= LinearizeExprTree(BO, Tree);
|
|
SmallVector<ValueEntry, 8> Factors;
|
|
Factors.reserve(Tree.size());
|
|
for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
|
|
RepeatedValue E = Tree[i];
|
|
Factors.append(E.second.getZExtValue(),
|
|
ValueEntry(getRank(E.first), E.first));
|
|
}
|
|
|
|
bool FoundFactor = false;
|
|
bool NeedsNegate = false;
|
|
for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
|
|
if (Factors[i].Op == Factor) {
|
|
FoundFactor = true;
|
|
Factors.erase(Factors.begin()+i);
|
|
break;
|
|
}
|
|
|
|
// If this is a negative version of this factor, remove it.
|
|
if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor)) {
|
|
if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
|
|
if (FC1->getValue() == -FC2->getValue()) {
|
|
FoundFactor = NeedsNegate = true;
|
|
Factors.erase(Factors.begin()+i);
|
|
break;
|
|
}
|
|
} else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) {
|
|
if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) {
|
|
const APFloat &F1 = FC1->getValueAPF();
|
|
APFloat F2(FC2->getValueAPF());
|
|
F2.changeSign();
|
|
if (F1 == F2) {
|
|
FoundFactor = NeedsNegate = true;
|
|
Factors.erase(Factors.begin() + i);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!FoundFactor) {
|
|
// Make sure to restore the operands to the expression tree.
|
|
RewriteExprTree(BO, Factors);
|
|
return nullptr;
|
|
}
|
|
|
|
BasicBlock::iterator InsertPt = ++BO->getIterator();
|
|
|
|
// If this was just a single multiply, remove the multiply and return the only
|
|
// remaining operand.
|
|
if (Factors.size() == 1) {
|
|
RedoInsts.insert(BO);
|
|
V = Factors[0].Op;
|
|
} else {
|
|
RewriteExprTree(BO, Factors);
|
|
V = BO;
|
|
}
|
|
|
|
if (NeedsNegate)
|
|
V = CreateNeg(V, "neg", &*InsertPt, BO);
|
|
|
|
return V;
|
|
}
|
|
|
|
/// If V is a single-use multiply, recursively add its operands as factors,
|
|
/// otherwise add V to the list of factors.
|
|
///
|
|
/// Ops is the top-level list of add operands we're trying to factor.
|
|
static void FindSingleUseMultiplyFactors(Value *V,
|
|
SmallVectorImpl<Value*> &Factors) {
|
|
BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
|
|
if (!BO) {
|
|
Factors.push_back(V);
|
|
return;
|
|
}
|
|
|
|
// Otherwise, add the LHS and RHS to the list of factors.
|
|
FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
|
|
FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
|
|
}
|
|
|
|
/// Optimize a series of operands to an 'and', 'or', or 'xor' instruction.
|
|
/// This optimizes based on identities. If it can be reduced to a single Value,
|
|
/// it is returned, otherwise the Ops list is mutated as necessary.
|
|
static Value *OptimizeAndOrXor(unsigned Opcode,
|
|
SmallVectorImpl<ValueEntry> &Ops) {
|
|
// Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
|
|
// If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
// First, check for X and ~X in the operand list.
|
|
assert(i < Ops.size());
|
|
Value *X;
|
|
if (match(Ops[i].Op, m_Not(m_Value(X)))) { // Cannot occur for ^.
|
|
unsigned FoundX = FindInOperandList(Ops, i, X);
|
|
if (FoundX != i) {
|
|
if (Opcode == Instruction::And) // ...&X&~X = 0
|
|
return Constant::getNullValue(X->getType());
|
|
|
|
if (Opcode == Instruction::Or) // ...|X|~X = -1
|
|
return Constant::getAllOnesValue(X->getType());
|
|
}
|
|
}
|
|
|
|
// Next, check for duplicate pairs of values, which we assume are next to
|
|
// each other, due to our sorting criteria.
|
|
assert(i < Ops.size());
|
|
if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
|
|
if (Opcode == Instruction::And || Opcode == Instruction::Or) {
|
|
// Drop duplicate values for And and Or.
|
|
Ops.erase(Ops.begin()+i);
|
|
--i; --e;
|
|
++NumAnnihil;
|
|
continue;
|
|
}
|
|
|
|
// Drop pairs of values for Xor.
|
|
assert(Opcode == Instruction::Xor);
|
|
if (e == 2)
|
|
return Constant::getNullValue(Ops[0].Op->getType());
|
|
|
|
// Y ^ X^X -> Y
|
|
Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
|
|
i -= 1; e -= 2;
|
|
++NumAnnihil;
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
/// Helper function of CombineXorOpnd(). It creates a bitwise-and
|
|
/// instruction with the given two operands, and return the resulting
|
|
/// instruction. There are two special cases: 1) if the constant operand is 0,
|
|
/// it will return NULL. 2) if the constant is ~0, the symbolic operand will
|
|
/// be returned.
|
|
static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
|
|
const APInt &ConstOpnd) {
|
|
if (ConstOpnd.isNullValue())
|
|
return nullptr;
|
|
|
|
if (ConstOpnd.isAllOnesValue())
|
|
return Opnd;
|
|
|
|
Instruction *I = BinaryOperator::CreateAnd(
|
|
Opnd, ConstantInt::get(Opnd->getType(), ConstOpnd), "and.ra",
|
|
InsertBefore);
|
|
I->setDebugLoc(InsertBefore->getDebugLoc());
|
|
return I;
|
|
}
|
|
|
|
// Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
|
|
// into "R ^ C", where C would be 0, and R is a symbolic value.
|
|
//
|
|
// If it was successful, true is returned, and the "R" and "C" is returned
|
|
// via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
|
|
// and both "Res" and "ConstOpnd" remain unchanged.
|
|
bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
|
|
APInt &ConstOpnd, Value *&Res) {
|
|
// Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
|
|
// = ((x | c1) ^ c1) ^ (c1 ^ c2)
|
|
// = (x & ~c1) ^ (c1 ^ c2)
|
|
// It is useful only when c1 == c2.
|
|
if (!Opnd1->isOrExpr() || Opnd1->getConstPart().isNullValue())
|
|
return false;
|
|
|
|
if (!Opnd1->getValue()->hasOneUse())
|
|
return false;
|
|
|
|
const APInt &C1 = Opnd1->getConstPart();
|
|
if (C1 != ConstOpnd)
|
|
return false;
|
|
|
|
Value *X = Opnd1->getSymbolicPart();
|
|
Res = createAndInstr(I, X, ~C1);
|
|
// ConstOpnd was C2, now C1 ^ C2.
|
|
ConstOpnd ^= C1;
|
|
|
|
if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
|
|
RedoInsts.insert(T);
|
|
return true;
|
|
}
|
|
|
|
// Helper function of OptimizeXor(). It tries to simplify
|
|
// "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
|
|
// symbolic value.
|
|
//
|
|
// If it was successful, true is returned, and the "R" and "C" is returned
|
|
// via "Res" and "ConstOpnd", respectively (If the entire expression is
|
|
// evaluated to a constant, the Res is set to NULL); otherwise, false is
|
|
// returned, and both "Res" and "ConstOpnd" remain unchanged.
|
|
bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
|
|
XorOpnd *Opnd2, APInt &ConstOpnd,
|
|
Value *&Res) {
|
|
Value *X = Opnd1->getSymbolicPart();
|
|
if (X != Opnd2->getSymbolicPart())
|
|
return false;
|
|
|
|
// This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
|
|
int DeadInstNum = 1;
|
|
if (Opnd1->getValue()->hasOneUse())
|
|
DeadInstNum++;
|
|
if (Opnd2->getValue()->hasOneUse())
|
|
DeadInstNum++;
|
|
|
|
// Xor-Rule 2:
|
|
// (x | c1) ^ (x & c2)
|
|
// = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
|
|
// = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
|
|
// = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
|
|
//
|
|
if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
|
|
if (Opnd2->isOrExpr())
|
|
std::swap(Opnd1, Opnd2);
|
|
|
|
const APInt &C1 = Opnd1->getConstPart();
|
|
const APInt &C2 = Opnd2->getConstPart();
|
|
APInt C3((~C1) ^ C2);
|
|
|
|
// Do not increase code size!
|
|
if (!C3.isNullValue() && !C3.isAllOnesValue()) {
|
|
int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
|
|
if (NewInstNum > DeadInstNum)
|
|
return false;
|
|
}
|
|
|
|
Res = createAndInstr(I, X, C3);
|
|
ConstOpnd ^= C1;
|
|
} else if (Opnd1->isOrExpr()) {
|
|
// Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
|
|
//
|
|
const APInt &C1 = Opnd1->getConstPart();
|
|
const APInt &C2 = Opnd2->getConstPart();
|
|
APInt C3 = C1 ^ C2;
|
|
|
|
// Do not increase code size
|
|
if (!C3.isNullValue() && !C3.isAllOnesValue()) {
|
|
int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
|
|
if (NewInstNum > DeadInstNum)
|
|
return false;
|
|
}
|
|
|
|
Res = createAndInstr(I, X, C3);
|
|
ConstOpnd ^= C3;
|
|
} else {
|
|
// Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
|
|
//
|
|
const APInt &C1 = Opnd1->getConstPart();
|
|
const APInt &C2 = Opnd2->getConstPart();
|
|
APInt C3 = C1 ^ C2;
|
|
Res = createAndInstr(I, X, C3);
|
|
}
|
|
|
|
// Put the original operands in the Redo list; hope they will be deleted
|
|
// as dead code.
|
|
if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
|
|
RedoInsts.insert(T);
|
|
if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
|
|
RedoInsts.insert(T);
|
|
|
|
return true;
|
|
}
|
|
|
|
/// Optimize a series of operands to an 'xor' instruction. If it can be reduced
|
|
/// to a single Value, it is returned, otherwise the Ops list is mutated as
|
|
/// necessary.
|
|
Value *ReassociatePass::OptimizeXor(Instruction *I,
|
|
SmallVectorImpl<ValueEntry> &Ops) {
|
|
if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
|
|
return V;
|
|
|
|
if (Ops.size() == 1)
|
|
return nullptr;
|
|
|
|
SmallVector<XorOpnd, 8> Opnds;
|
|
SmallVector<XorOpnd*, 8> OpndPtrs;
|
|
Type *Ty = Ops[0].Op->getType();
|
|
APInt ConstOpnd(Ty->getScalarSizeInBits(), 0);
|
|
|
|
// Step 1: Convert ValueEntry to XorOpnd
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
Value *V = Ops[i].Op;
|
|
const APInt *C;
|
|
// TODO: Support non-splat vectors.
|
|
if (match(V, m_APInt(C))) {
|
|
ConstOpnd ^= *C;
|
|
} else {
|
|
XorOpnd O(V);
|
|
O.setSymbolicRank(getRank(O.getSymbolicPart()));
|
|
Opnds.push_back(O);
|
|
}
|
|
}
|
|
|
|
// NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
|
|
// It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
|
|
// the "OpndPtrs" as well. For the similar reason, do not fuse this loop
|
|
// with the previous loop --- the iterator of the "Opnds" may be invalidated
|
|
// when new elements are added to the vector.
|
|
for (unsigned i = 0, e = Opnds.size(); i != e; ++i)
|
|
OpndPtrs.push_back(&Opnds[i]);
|
|
|
|
// Step 2: Sort the Xor-Operands in a way such that the operands containing
|
|
// the same symbolic value cluster together. For instance, the input operand
|
|
// sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
|
|
// ("x | 123", "x & 789", "y & 456").
|
|
//
|
|
// The purpose is twofold:
|
|
// 1) Cluster together the operands sharing the same symbolic-value.
|
|
// 2) Operand having smaller symbolic-value-rank is permuted earlier, which
|
|
// could potentially shorten crital path, and expose more loop-invariants.
|
|
// Note that values' rank are basically defined in RPO order (FIXME).
|
|
// So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
|
|
// than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
|
|
// "z" in the order of X-Y-Z is better than any other orders.
|
|
llvm::stable_sort(OpndPtrs, [](XorOpnd *LHS, XorOpnd *RHS) {
|
|
return LHS->getSymbolicRank() < RHS->getSymbolicRank();
|
|
});
|
|
|
|
// Step 3: Combine adjacent operands
|
|
XorOpnd *PrevOpnd = nullptr;
|
|
bool Changed = false;
|
|
for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
|
|
XorOpnd *CurrOpnd = OpndPtrs[i];
|
|
// The combined value
|
|
Value *CV;
|
|
|
|
// Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
|
|
if (!ConstOpnd.isNullValue() &&
|
|
CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
|
|
Changed = true;
|
|
if (CV)
|
|
*CurrOpnd = XorOpnd(CV);
|
|
else {
|
|
CurrOpnd->Invalidate();
|
|
continue;
|
|
}
|
|
}
|
|
|
|
if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
|
|
PrevOpnd = CurrOpnd;
|
|
continue;
|
|
}
|
|
|
|
// step 3.2: When previous and current operands share the same symbolic
|
|
// value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
|
|
if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
|
|
// Remove previous operand
|
|
PrevOpnd->Invalidate();
|
|
if (CV) {
|
|
*CurrOpnd = XorOpnd(CV);
|
|
PrevOpnd = CurrOpnd;
|
|
} else {
|
|
CurrOpnd->Invalidate();
|
|
PrevOpnd = nullptr;
|
|
}
|
|
Changed = true;
|
|
}
|
|
}
|
|
|
|
// Step 4: Reassemble the Ops
|
|
if (Changed) {
|
|
Ops.clear();
|
|
for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
|
|
XorOpnd &O = Opnds[i];
|
|
if (O.isInvalid())
|
|
continue;
|
|
ValueEntry VE(getRank(O.getValue()), O.getValue());
|
|
Ops.push_back(VE);
|
|
}
|
|
if (!ConstOpnd.isNullValue()) {
|
|
Value *C = ConstantInt::get(Ty, ConstOpnd);
|
|
ValueEntry VE(getRank(C), C);
|
|
Ops.push_back(VE);
|
|
}
|
|
unsigned Sz = Ops.size();
|
|
if (Sz == 1)
|
|
return Ops.back().Op;
|
|
if (Sz == 0) {
|
|
assert(ConstOpnd.isNullValue());
|
|
return ConstantInt::get(Ty, ConstOpnd);
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Optimize a series of operands to an 'add' instruction. This
|
|
/// optimizes based on identities. If it can be reduced to a single Value, it
|
|
/// is returned, otherwise the Ops list is mutated as necessary.
|
|
Value *ReassociatePass::OptimizeAdd(Instruction *I,
|
|
SmallVectorImpl<ValueEntry> &Ops) {
|
|
// Scan the operand lists looking for X and -X pairs. If we find any, we
|
|
// can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
|
|
// scan for any
|
|
// duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
|
|
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
Value *TheOp = Ops[i].Op;
|
|
// Check to see if we've seen this operand before. If so, we factor all
|
|
// instances of the operand together. Due to our sorting criteria, we know
|
|
// that these need to be next to each other in the vector.
|
|
if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
|
|
// Rescan the list, remove all instances of this operand from the expr.
|
|
unsigned NumFound = 0;
|
|
do {
|
|
Ops.erase(Ops.begin()+i);
|
|
++NumFound;
|
|
} while (i != Ops.size() && Ops[i].Op == TheOp);
|
|
|
|
LLVM_DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp
|
|
<< '\n');
|
|
++NumFactor;
|
|
|
|
// Insert a new multiply.
|
|
Type *Ty = TheOp->getType();
|
|
Constant *C = Ty->isIntOrIntVectorTy() ?
|
|
ConstantInt::get(Ty, NumFound) : ConstantFP::get(Ty, NumFound);
|
|
Instruction *Mul = CreateMul(TheOp, C, "factor", I, I);
|
|
|
|
// Now that we have inserted a multiply, optimize it. This allows us to
|
|
// handle cases that require multiple factoring steps, such as this:
|
|
// (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
|
|
RedoInsts.insert(Mul);
|
|
|
|
// If every add operand was a duplicate, return the multiply.
|
|
if (Ops.empty())
|
|
return Mul;
|
|
|
|
// Otherwise, we had some input that didn't have the dupe, such as
|
|
// "A + A + B" -> "A*2 + B". Add the new multiply to the list of
|
|
// things being added by this operation.
|
|
Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
|
|
|
|
--i;
|
|
e = Ops.size();
|
|
continue;
|
|
}
|
|
|
|
// Check for X and -X or X and ~X in the operand list.
|
|
Value *X;
|
|
if (!match(TheOp, m_Neg(m_Value(X))) && !match(TheOp, m_Not(m_Value(X))) &&
|
|
!match(TheOp, m_FNeg(m_Value(X))))
|
|
continue;
|
|
|
|
unsigned FoundX = FindInOperandList(Ops, i, X);
|
|
if (FoundX == i)
|
|
continue;
|
|
|
|
// Remove X and -X from the operand list.
|
|
if (Ops.size() == 2 &&
|
|
(match(TheOp, m_Neg(m_Value())) || match(TheOp, m_FNeg(m_Value()))))
|
|
return Constant::getNullValue(X->getType());
|
|
|
|
// Remove X and ~X from the operand list.
|
|
if (Ops.size() == 2 && match(TheOp, m_Not(m_Value())))
|
|
return Constant::getAllOnesValue(X->getType());
|
|
|
|
Ops.erase(Ops.begin()+i);
|
|
if (i < FoundX)
|
|
--FoundX;
|
|
else
|
|
--i; // Need to back up an extra one.
|
|
Ops.erase(Ops.begin()+FoundX);
|
|
++NumAnnihil;
|
|
--i; // Revisit element.
|
|
e -= 2; // Removed two elements.
|
|
|
|
// if X and ~X we append -1 to the operand list.
|
|
if (match(TheOp, m_Not(m_Value()))) {
|
|
Value *V = Constant::getAllOnesValue(X->getType());
|
|
Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
|
|
e += 1;
|
|
}
|
|
}
|
|
|
|
// Scan the operand list, checking to see if there are any common factors
|
|
// between operands. Consider something like A*A+A*B*C+D. We would like to
|
|
// reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
|
|
// To efficiently find this, we count the number of times a factor occurs
|
|
// for any ADD operands that are MULs.
|
|
DenseMap<Value*, unsigned> FactorOccurrences;
|
|
|
|
// Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
|
|
// where they are actually the same multiply.
|
|
unsigned MaxOcc = 0;
|
|
Value *MaxOccVal = nullptr;
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
BinaryOperator *BOp =
|
|
isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
|
|
if (!BOp)
|
|
continue;
|
|
|
|
// Compute all of the factors of this added value.
|
|
SmallVector<Value*, 8> Factors;
|
|
FindSingleUseMultiplyFactors(BOp, Factors);
|
|
assert(Factors.size() > 1 && "Bad linearize!");
|
|
|
|
// Add one to FactorOccurrences for each unique factor in this op.
|
|
SmallPtrSet<Value*, 8> Duplicates;
|
|
for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
|
|
Value *Factor = Factors[i];
|
|
if (!Duplicates.insert(Factor).second)
|
|
continue;
|
|
|
|
unsigned Occ = ++FactorOccurrences[Factor];
|
|
if (Occ > MaxOcc) {
|
|
MaxOcc = Occ;
|
|
MaxOccVal = Factor;
|
|
}
|
|
|
|
// If Factor is a negative constant, add the negated value as a factor
|
|
// because we can percolate the negate out. Watch for minint, which
|
|
// cannot be positivified.
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor)) {
|
|
if (CI->isNegative() && !CI->isMinValue(true)) {
|
|
Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
|
|
if (!Duplicates.insert(Factor).second)
|
|
continue;
|
|
unsigned Occ = ++FactorOccurrences[Factor];
|
|
if (Occ > MaxOcc) {
|
|
MaxOcc = Occ;
|
|
MaxOccVal = Factor;
|
|
}
|
|
}
|
|
} else if (ConstantFP *CF = dyn_cast<ConstantFP>(Factor)) {
|
|
if (CF->isNegative()) {
|
|
APFloat F(CF->getValueAPF());
|
|
F.changeSign();
|
|
Factor = ConstantFP::get(CF->getContext(), F);
|
|
if (!Duplicates.insert(Factor).second)
|
|
continue;
|
|
unsigned Occ = ++FactorOccurrences[Factor];
|
|
if (Occ > MaxOcc) {
|
|
MaxOcc = Occ;
|
|
MaxOccVal = Factor;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// If any factor occurred more than one time, we can pull it out.
|
|
if (MaxOcc > 1) {
|
|
LLVM_DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal
|
|
<< '\n');
|
|
++NumFactor;
|
|
|
|
// Create a new instruction that uses the MaxOccVal twice. If we don't do
|
|
// this, we could otherwise run into situations where removing a factor
|
|
// from an expression will drop a use of maxocc, and this can cause
|
|
// RemoveFactorFromExpression on successive values to behave differently.
|
|
Instruction *DummyInst =
|
|
I->getType()->isIntOrIntVectorTy()
|
|
? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
|
|
: BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
|
|
|
|
SmallVector<WeakTrackingVH, 4> NewMulOps;
|
|
for (unsigned i = 0; i != Ops.size(); ++i) {
|
|
// Only try to remove factors from expressions we're allowed to.
|
|
BinaryOperator *BOp =
|
|
isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
|
|
if (!BOp)
|
|
continue;
|
|
|
|
if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
|
|
// The factorized operand may occur several times. Convert them all in
|
|
// one fell swoop.
|
|
for (unsigned j = Ops.size(); j != i;) {
|
|
--j;
|
|
if (Ops[j].Op == Ops[i].Op) {
|
|
NewMulOps.push_back(V);
|
|
Ops.erase(Ops.begin()+j);
|
|
}
|
|
}
|
|
--i;
|
|
}
|
|
}
|
|
|
|
// No need for extra uses anymore.
|
|
DummyInst->deleteValue();
|
|
|
|
unsigned NumAddedValues = NewMulOps.size();
|
|
Value *V = EmitAddTreeOfValues(I, NewMulOps);
|
|
|
|
// Now that we have inserted the add tree, optimize it. This allows us to
|
|
// handle cases that require multiple factoring steps, such as this:
|
|
// A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
|
|
assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
|
|
(void)NumAddedValues;
|
|
if (Instruction *VI = dyn_cast<Instruction>(V))
|
|
RedoInsts.insert(VI);
|
|
|
|
// Create the multiply.
|
|
Instruction *V2 = CreateMul(V, MaxOccVal, "reass.mul", I, I);
|
|
|
|
// Rerun associate on the multiply in case the inner expression turned into
|
|
// a multiply. We want to make sure that we keep things in canonical form.
|
|
RedoInsts.insert(V2);
|
|
|
|
// If every add operand included the factor (e.g. "A*B + A*C"), then the
|
|
// entire result expression is just the multiply "A*(B+C)".
|
|
if (Ops.empty())
|
|
return V2;
|
|
|
|
// Otherwise, we had some input that didn't have the factor, such as
|
|
// "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
|
|
// things being added by this operation.
|
|
Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Build up a vector of value/power pairs factoring a product.
|
|
///
|
|
/// Given a series of multiplication operands, build a vector of factors and
|
|
/// the powers each is raised to when forming the final product. Sort them in
|
|
/// the order of descending power.
|
|
///
|
|
/// (x*x) -> [(x, 2)]
|
|
/// ((x*x)*x) -> [(x, 3)]
|
|
/// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
|
|
///
|
|
/// \returns Whether any factors have a power greater than one.
|
|
static bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
|
|
SmallVectorImpl<Factor> &Factors) {
|
|
// FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
|
|
// Compute the sum of powers of simplifiable factors.
|
|
unsigned FactorPowerSum = 0;
|
|
for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
|
|
Value *Op = Ops[Idx-1].Op;
|
|
|
|
// Count the number of occurrences of this value.
|
|
unsigned Count = 1;
|
|
for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
|
|
++Count;
|
|
// Track for simplification all factors which occur 2 or more times.
|
|
if (Count > 1)
|
|
FactorPowerSum += Count;
|
|
}
|
|
|
|
// We can only simplify factors if the sum of the powers of our simplifiable
|
|
// factors is 4 or higher. When that is the case, we will *always* have
|
|
// a simplification. This is an important invariant to prevent cyclicly
|
|
// trying to simplify already minimal formations.
|
|
if (FactorPowerSum < 4)
|
|
return false;
|
|
|
|
// Now gather the simplifiable factors, removing them from Ops.
|
|
FactorPowerSum = 0;
|
|
for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
|
|
Value *Op = Ops[Idx-1].Op;
|
|
|
|
// Count the number of occurrences of this value.
|
|
unsigned Count = 1;
|
|
for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
|
|
++Count;
|
|
if (Count == 1)
|
|
continue;
|
|
// Move an even number of occurrences to Factors.
|
|
Count &= ~1U;
|
|
Idx -= Count;
|
|
FactorPowerSum += Count;
|
|
Factors.push_back(Factor(Op, Count));
|
|
Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
|
|
}
|
|
|
|
// None of the adjustments above should have reduced the sum of factor powers
|
|
// below our mininum of '4'.
|
|
assert(FactorPowerSum >= 4);
|
|
|
|
llvm::stable_sort(Factors, [](const Factor &LHS, const Factor &RHS) {
|
|
return LHS.Power > RHS.Power;
|
|
});
|
|
return true;
|
|
}
|
|
|
|
/// Build a tree of multiplies, computing the product of Ops.
|
|
static Value *buildMultiplyTree(IRBuilderBase &Builder,
|
|
SmallVectorImpl<Value*> &Ops) {
|
|
if (Ops.size() == 1)
|
|
return Ops.back();
|
|
|
|
Value *LHS = Ops.pop_back_val();
|
|
do {
|
|
if (LHS->getType()->isIntOrIntVectorTy())
|
|
LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
|
|
else
|
|
LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
|
|
} while (!Ops.empty());
|
|
|
|
return LHS;
|
|
}
|
|
|
|
/// Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
|
|
///
|
|
/// Given a vector of values raised to various powers, where no two values are
|
|
/// equal and the powers are sorted in decreasing order, compute the minimal
|
|
/// DAG of multiplies to compute the final product, and return that product
|
|
/// value.
|
|
Value *
|
|
ReassociatePass::buildMinimalMultiplyDAG(IRBuilderBase &Builder,
|
|
SmallVectorImpl<Factor> &Factors) {
|
|
assert(Factors[0].Power);
|
|
SmallVector<Value *, 4> OuterProduct;
|
|
for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
|
|
Idx < Size && Factors[Idx].Power > 0; ++Idx) {
|
|
if (Factors[Idx].Power != Factors[LastIdx].Power) {
|
|
LastIdx = Idx;
|
|
continue;
|
|
}
|
|
|
|
// We want to multiply across all the factors with the same power so that
|
|
// we can raise them to that power as a single entity. Build a mini tree
|
|
// for that.
|
|
SmallVector<Value *, 4> InnerProduct;
|
|
InnerProduct.push_back(Factors[LastIdx].Base);
|
|
do {
|
|
InnerProduct.push_back(Factors[Idx].Base);
|
|
++Idx;
|
|
} while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
|
|
|
|
// Reset the base value of the first factor to the new expression tree.
|
|
// We'll remove all the factors with the same power in a second pass.
|
|
Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
|
|
if (Instruction *MI = dyn_cast<Instruction>(M))
|
|
RedoInsts.insert(MI);
|
|
|
|
LastIdx = Idx;
|
|
}
|
|
// Unique factors with equal powers -- we've folded them into the first one's
|
|
// base.
|
|
Factors.erase(std::unique(Factors.begin(), Factors.end(),
|
|
[](const Factor &LHS, const Factor &RHS) {
|
|
return LHS.Power == RHS.Power;
|
|
}),
|
|
Factors.end());
|
|
|
|
// Iteratively collect the base of each factor with an add power into the
|
|
// outer product, and halve each power in preparation for squaring the
|
|
// expression.
|
|
for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
|
|
if (Factors[Idx].Power & 1)
|
|
OuterProduct.push_back(Factors[Idx].Base);
|
|
Factors[Idx].Power >>= 1;
|
|
}
|
|
if (Factors[0].Power) {
|
|
Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
|
|
OuterProduct.push_back(SquareRoot);
|
|
OuterProduct.push_back(SquareRoot);
|
|
}
|
|
if (OuterProduct.size() == 1)
|
|
return OuterProduct.front();
|
|
|
|
Value *V = buildMultiplyTree(Builder, OuterProduct);
|
|
return V;
|
|
}
|
|
|
|
Value *ReassociatePass::OptimizeMul(BinaryOperator *I,
|
|
SmallVectorImpl<ValueEntry> &Ops) {
|
|
// We can only optimize the multiplies when there is a chain of more than
|
|
// three, such that a balanced tree might require fewer total multiplies.
|
|
if (Ops.size() < 4)
|
|
return nullptr;
|
|
|
|
// Try to turn linear trees of multiplies without other uses of the
|
|
// intermediate stages into minimal multiply DAGs with perfect sub-expression
|
|
// re-use.
|
|
SmallVector<Factor, 4> Factors;
|
|
if (!collectMultiplyFactors(Ops, Factors))
|
|
return nullptr; // All distinct factors, so nothing left for us to do.
|
|
|
|
IRBuilder<> Builder(I);
|
|
// The reassociate transformation for FP operations is performed only
|
|
// if unsafe algebra is permitted by FastMathFlags. Propagate those flags
|
|
// to the newly generated operations.
|
|
if (auto FPI = dyn_cast<FPMathOperator>(I))
|
|
Builder.setFastMathFlags(FPI->getFastMathFlags());
|
|
|
|
Value *V = buildMinimalMultiplyDAG(Builder, Factors);
|
|
if (Ops.empty())
|
|
return V;
|
|
|
|
ValueEntry NewEntry = ValueEntry(getRank(V), V);
|
|
Ops.insert(llvm::lower_bound(Ops, NewEntry), NewEntry);
|
|
return nullptr;
|
|
}
|
|
|
|
Value *ReassociatePass::OptimizeExpression(BinaryOperator *I,
|
|
SmallVectorImpl<ValueEntry> &Ops) {
|
|
// Now that we have the linearized expression tree, try to optimize it.
|
|
// Start by folding any constants that we found.
|
|
Constant *Cst = nullptr;
|
|
unsigned Opcode = I->getOpcode();
|
|
while (!Ops.empty() && isa<Constant>(Ops.back().Op)) {
|
|
Constant *C = cast<Constant>(Ops.pop_back_val().Op);
|
|
Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C;
|
|
}
|
|
// If there was nothing but constants then we are done.
|
|
if (Ops.empty())
|
|
return Cst;
|
|
|
|
// Put the combined constant back at the end of the operand list, except if
|
|
// there is no point. For example, an add of 0 gets dropped here, while a
|
|
// multiplication by zero turns the whole expression into zero.
|
|
if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
|
|
if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
|
|
return Cst;
|
|
Ops.push_back(ValueEntry(0, Cst));
|
|
}
|
|
|
|
if (Ops.size() == 1) return Ops[0].Op;
|
|
|
|
// Handle destructive annihilation due to identities between elements in the
|
|
// argument list here.
|
|
unsigned NumOps = Ops.size();
|
|
switch (Opcode) {
|
|
default: break;
|
|
case Instruction::And:
|
|
case Instruction::Or:
|
|
if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
|
|
return Result;
|
|
break;
|
|
|
|
case Instruction::Xor:
|
|
if (Value *Result = OptimizeXor(I, Ops))
|
|
return Result;
|
|
break;
|
|
|
|
case Instruction::Add:
|
|
case Instruction::FAdd:
|
|
if (Value *Result = OptimizeAdd(I, Ops))
|
|
return Result;
|
|
break;
|
|
|
|
case Instruction::Mul:
|
|
case Instruction::FMul:
|
|
if (Value *Result = OptimizeMul(I, Ops))
|
|
return Result;
|
|
break;
|
|
}
|
|
|
|
if (Ops.size() != NumOps)
|
|
return OptimizeExpression(I, Ops);
|
|
return nullptr;
|
|
}
|
|
|
|
// Remove dead instructions and if any operands are trivially dead add them to
|
|
// Insts so they will be removed as well.
|
|
void ReassociatePass::RecursivelyEraseDeadInsts(Instruction *I,
|
|
OrderedSet &Insts) {
|
|
assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
|
|
SmallVector<Value *, 4> Ops(I->operands());
|
|
ValueRankMap.erase(I);
|
|
Insts.remove(I);
|
|
RedoInsts.remove(I);
|
|
llvm::salvageDebugInfo(*I);
|
|
I->eraseFromParent();
|
|
for (auto Op : Ops)
|
|
if (Instruction *OpInst = dyn_cast<Instruction>(Op))
|
|
if (OpInst->use_empty())
|
|
Insts.insert(OpInst);
|
|
}
|
|
|
|
/// Zap the given instruction, adding interesting operands to the work list.
|
|
void ReassociatePass::EraseInst(Instruction *I) {
|
|
assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
|
|
LLVM_DEBUG(dbgs() << "Erasing dead inst: "; I->dump());
|
|
|
|
SmallVector<Value *, 8> Ops(I->operands());
|
|
// Erase the dead instruction.
|
|
ValueRankMap.erase(I);
|
|
RedoInsts.remove(I);
|
|
llvm::salvageDebugInfo(*I);
|
|
I->eraseFromParent();
|
|
// Optimize its operands.
|
|
SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
|
|
if (Instruction *Op = dyn_cast<Instruction>(Ops[i])) {
|
|
// If this is a node in an expression tree, climb to the expression root
|
|
// and add that since that's where optimization actually happens.
|
|
unsigned Opcode = Op->getOpcode();
|
|
while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
|
|
Visited.insert(Op).second)
|
|
Op = Op->user_back();
|
|
|
|
// The instruction we're going to push may be coming from a
|
|
// dead block, and Reassociate skips the processing of unreachable
|
|
// blocks because it's a waste of time and also because it can
|
|
// lead to infinite loop due to LLVM's non-standard definition
|
|
// of dominance.
|
|
if (ValueRankMap.find(Op) != ValueRankMap.end())
|
|
RedoInsts.insert(Op);
|
|
}
|
|
|
|
MadeChange = true;
|
|
}
|
|
|
|
/// Recursively analyze an expression to build a list of instructions that have
|
|
/// negative floating-point constant operands. The caller can then transform
|
|
/// the list to create positive constants for better reassociation and CSE.
|
|
static void getNegatibleInsts(Value *V,
|
|
SmallVectorImpl<Instruction *> &Candidates) {
|
|
// Handle only one-use instructions. Combining negations does not justify
|
|
// replicating instructions.
|
|
Instruction *I;
|
|
if (!match(V, m_OneUse(m_Instruction(I))))
|
|
return;
|
|
|
|
// Handle expressions of multiplications and divisions.
|
|
// TODO: This could look through floating-point casts.
|
|
const APFloat *C;
|
|
switch (I->getOpcode()) {
|
|
case Instruction::FMul:
|
|
// Not expecting non-canonical code here. Bail out and wait.
|
|
if (match(I->getOperand(0), m_Constant()))
|
|
break;
|
|
|
|
if (match(I->getOperand(1), m_APFloat(C)) && C->isNegative()) {
|
|
Candidates.push_back(I);
|
|
LLVM_DEBUG(dbgs() << "FMul with negative constant: " << *I << '\n');
|
|
}
|
|
getNegatibleInsts(I->getOperand(0), Candidates);
|
|
getNegatibleInsts(I->getOperand(1), Candidates);
|
|
break;
|
|
case Instruction::FDiv:
|
|
// Not expecting non-canonical code here. Bail out and wait.
|
|
if (match(I->getOperand(0), m_Constant()) &&
|
|
match(I->getOperand(1), m_Constant()))
|
|
break;
|
|
|
|
if ((match(I->getOperand(0), m_APFloat(C)) && C->isNegative()) ||
|
|
(match(I->getOperand(1), m_APFloat(C)) && C->isNegative())) {
|
|
Candidates.push_back(I);
|
|
LLVM_DEBUG(dbgs() << "FDiv with negative constant: " << *I << '\n');
|
|
}
|
|
getNegatibleInsts(I->getOperand(0), Candidates);
|
|
getNegatibleInsts(I->getOperand(1), Candidates);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
/// Given an fadd/fsub with an operand that is a one-use instruction
|
|
/// (the fadd/fsub), try to change negative floating-point constants into
|
|
/// positive constants to increase potential for reassociation and CSE.
|
|
Instruction *ReassociatePass::canonicalizeNegFPConstantsForOp(Instruction *I,
|
|
Instruction *Op,
|
|
Value *OtherOp) {
|
|
assert((I->getOpcode() == Instruction::FAdd ||
|
|
I->getOpcode() == Instruction::FSub) && "Expected fadd/fsub");
|
|
|
|
// Collect instructions with negative FP constants from the subtree that ends
|
|
// in Op.
|
|
SmallVector<Instruction *, 4> Candidates;
|
|
getNegatibleInsts(Op, Candidates);
|
|
if (Candidates.empty())
|
|
return nullptr;
|
|
|
|
// Don't canonicalize x + (-Constant * y) -> x - (Constant * y), if the
|
|
// resulting subtract will be broken up later. This can get us into an
|
|
// infinite loop during reassociation.
|
|
bool IsFSub = I->getOpcode() == Instruction::FSub;
|
|
bool NeedsSubtract = !IsFSub && Candidates.size() % 2 == 1;
|
|
if (NeedsSubtract && ShouldBreakUpSubtract(I))
|
|
return nullptr;
|
|
|
|
for (Instruction *Negatible : Candidates) {
|
|
const APFloat *C;
|
|
if (match(Negatible->getOperand(0), m_APFloat(C))) {
|
|
assert(!match(Negatible->getOperand(1), m_Constant()) &&
|
|
"Expecting only 1 constant operand");
|
|
assert(C->isNegative() && "Expected negative FP constant");
|
|
Negatible->setOperand(0, ConstantFP::get(Negatible->getType(), abs(*C)));
|
|
MadeChange = true;
|
|
}
|
|
if (match(Negatible->getOperand(1), m_APFloat(C))) {
|
|
assert(!match(Negatible->getOperand(0), m_Constant()) &&
|
|
"Expecting only 1 constant operand");
|
|
assert(C->isNegative() && "Expected negative FP constant");
|
|
Negatible->setOperand(1, ConstantFP::get(Negatible->getType(), abs(*C)));
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
assert(MadeChange == true && "Negative constant candidate was not changed");
|
|
|
|
// Negations cancelled out.
|
|
if (Candidates.size() % 2 == 0)
|
|
return I;
|
|
|
|
// Negate the final operand in the expression by flipping the opcode of this
|
|
// fadd/fsub.
|
|
assert(Candidates.size() % 2 == 1 && "Expected odd number");
|
|
IRBuilder<> Builder(I);
|
|
Value *NewInst = IsFSub ? Builder.CreateFAddFMF(OtherOp, Op, I)
|
|
: Builder.CreateFSubFMF(OtherOp, Op, I);
|
|
I->replaceAllUsesWith(NewInst);
|
|
RedoInsts.insert(I);
|
|
return dyn_cast<Instruction>(NewInst);
|
|
}
|
|
|
|
/// Canonicalize expressions that contain a negative floating-point constant
|
|
/// of the following form:
|
|
/// OtherOp + (subtree) -> OtherOp {+/-} (canonical subtree)
|
|
/// (subtree) + OtherOp -> OtherOp {+/-} (canonical subtree)
|
|
/// OtherOp - (subtree) -> OtherOp {+/-} (canonical subtree)
|
|
///
|
|
/// The fadd/fsub opcode may be switched to allow folding a negation into the
|
|
/// input instruction.
|
|
Instruction *ReassociatePass::canonicalizeNegFPConstants(Instruction *I) {
|
|
LLVM_DEBUG(dbgs() << "Combine negations for: " << *I << '\n');
|
|
Value *X;
|
|
Instruction *Op;
|
|
if (match(I, m_FAdd(m_Value(X), m_OneUse(m_Instruction(Op)))))
|
|
if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
|
|
I = R;
|
|
if (match(I, m_FAdd(m_OneUse(m_Instruction(Op)), m_Value(X))))
|
|
if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
|
|
I = R;
|
|
if (match(I, m_FSub(m_Value(X), m_OneUse(m_Instruction(Op)))))
|
|
if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
|
|
I = R;
|
|
return I;
|
|
}
|
|
|
|
/// Inspect and optimize the given instruction. Note that erasing
|
|
/// instructions is not allowed.
|
|
void ReassociatePass::OptimizeInst(Instruction *I) {
|
|
// Only consider operations that we understand.
|
|
if (!isa<UnaryOperator>(I) && !isa<BinaryOperator>(I))
|
|
return;
|
|
|
|
if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(I->getOperand(1)))
|
|
// If an operand of this shift is a reassociable multiply, or if the shift
|
|
// is used by a reassociable multiply or add, turn into a multiply.
|
|
if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
|
|
(I->hasOneUse() &&
|
|
(isReassociableOp(I->user_back(), Instruction::Mul) ||
|
|
isReassociableOp(I->user_back(), Instruction::Add)))) {
|
|
Instruction *NI = ConvertShiftToMul(I);
|
|
RedoInsts.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
}
|
|
|
|
// Commute binary operators, to canonicalize the order of their operands.
|
|
// This can potentially expose more CSE opportunities, and makes writing other
|
|
// transformations simpler.
|
|
if (I->isCommutative())
|
|
canonicalizeOperands(I);
|
|
|
|
// Canonicalize negative constants out of expressions.
|
|
if (Instruction *Res = canonicalizeNegFPConstants(I))
|
|
I = Res;
|
|
|
|
// Don't optimize floating-point instructions unless they are 'fast'.
|
|
if (I->getType()->isFPOrFPVectorTy() && !I->isFast())
|
|
return;
|
|
|
|
// Do not reassociate boolean (i1) expressions. We want to preserve the
|
|
// original order of evaluation for short-circuited comparisons that
|
|
// SimplifyCFG has folded to AND/OR expressions. If the expression
|
|
// is not further optimized, it is likely to be transformed back to a
|
|
// short-circuited form for code gen, and the source order may have been
|
|
// optimized for the most likely conditions.
|
|
if (I->getType()->isIntegerTy(1))
|
|
return;
|
|
|
|
// If this is a bitwise or instruction of operands
|
|
// with no common bits set, convert it to X+Y.
|
|
if (I->getOpcode() == Instruction::Or &&
|
|
shouldConvertOrWithNoCommonBitsToAdd(I) && !isLoadCombineCandidate(I) &&
|
|
haveNoCommonBitsSet(I->getOperand(0), I->getOperand(1),
|
|
I->getModule()->getDataLayout(), /*AC=*/nullptr, I,
|
|
/*DT=*/nullptr)) {
|
|
Instruction *NI = convertOrWithNoCommonBitsToAdd(I);
|
|
RedoInsts.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
}
|
|
|
|
// If this is a subtract instruction which is not already in negate form,
|
|
// see if we can convert it to X+-Y.
|
|
if (I->getOpcode() == Instruction::Sub) {
|
|
if (ShouldBreakUpSubtract(I)) {
|
|
Instruction *NI = BreakUpSubtract(I, RedoInsts);
|
|
RedoInsts.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
} else if (match(I, m_Neg(m_Value()))) {
|
|
// Otherwise, this is a negation. See if the operand is a multiply tree
|
|
// and if this is not an inner node of a multiply tree.
|
|
if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
|
|
(!I->hasOneUse() ||
|
|
!isReassociableOp(I->user_back(), Instruction::Mul))) {
|
|
Instruction *NI = LowerNegateToMultiply(I);
|
|
// If the negate was simplified, revisit the users to see if we can
|
|
// reassociate further.
|
|
for (User *U : NI->users()) {
|
|
if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
|
|
RedoInsts.insert(Tmp);
|
|
}
|
|
RedoInsts.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
}
|
|
}
|
|
} else if (I->getOpcode() == Instruction::FNeg ||
|
|
I->getOpcode() == Instruction::FSub) {
|
|
if (ShouldBreakUpSubtract(I)) {
|
|
Instruction *NI = BreakUpSubtract(I, RedoInsts);
|
|
RedoInsts.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
} else if (match(I, m_FNeg(m_Value()))) {
|
|
// Otherwise, this is a negation. See if the operand is a multiply tree
|
|
// and if this is not an inner node of a multiply tree.
|
|
Value *Op = isa<BinaryOperator>(I) ? I->getOperand(1) :
|
|
I->getOperand(0);
|
|
if (isReassociableOp(Op, Instruction::FMul) &&
|
|
(!I->hasOneUse() ||
|
|
!isReassociableOp(I->user_back(), Instruction::FMul))) {
|
|
// If the negate was simplified, revisit the users to see if we can
|
|
// reassociate further.
|
|
Instruction *NI = LowerNegateToMultiply(I);
|
|
for (User *U : NI->users()) {
|
|
if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
|
|
RedoInsts.insert(Tmp);
|
|
}
|
|
RedoInsts.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
}
|
|
}
|
|
}
|
|
|
|
// If this instruction is an associative binary operator, process it.
|
|
if (!I->isAssociative()) return;
|
|
BinaryOperator *BO = cast<BinaryOperator>(I);
|
|
|
|
// If this is an interior node of a reassociable tree, ignore it until we
|
|
// get to the root of the tree, to avoid N^2 analysis.
|
|
unsigned Opcode = BO->getOpcode();
|
|
if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode) {
|
|
// During the initial run we will get to the root of the tree.
|
|
// But if we get here while we are redoing instructions, there is no
|
|
// guarantee that the root will be visited. So Redo later
|
|
if (BO->user_back() != BO &&
|
|
BO->getParent() == BO->user_back()->getParent())
|
|
RedoInsts.insert(BO->user_back());
|
|
return;
|
|
}
|
|
|
|
// If this is an add tree that is used by a sub instruction, ignore it
|
|
// until we process the subtract.
|
|
if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
|
|
cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
|
|
return;
|
|
if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd &&
|
|
cast<Instruction>(BO->user_back())->getOpcode() == Instruction::FSub)
|
|
return;
|
|
|
|
ReassociateExpression(BO);
|
|
}
|
|
|
|
void ReassociatePass::ReassociateExpression(BinaryOperator *I) {
|
|
// First, walk the expression tree, linearizing the tree, collecting the
|
|
// operand information.
|
|
SmallVector<RepeatedValue, 8> Tree;
|
|
MadeChange |= LinearizeExprTree(I, Tree);
|
|
SmallVector<ValueEntry, 8> Ops;
|
|
Ops.reserve(Tree.size());
|
|
for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
|
|
RepeatedValue E = Tree[i];
|
|
Ops.append(E.second.getZExtValue(),
|
|
ValueEntry(getRank(E.first), E.first));
|
|
}
|
|
|
|
LLVM_DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
|
|
|
|
// Now that we have linearized the tree to a list and have gathered all of
|
|
// the operands and their ranks, sort the operands by their rank. Use a
|
|
// stable_sort so that values with equal ranks will have their relative
|
|
// positions maintained (and so the compiler is deterministic). Note that
|
|
// this sorts so that the highest ranking values end up at the beginning of
|
|
// the vector.
|
|
llvm::stable_sort(Ops);
|
|
|
|
// Now that we have the expression tree in a convenient
|
|
// sorted form, optimize it globally if possible.
|
|
if (Value *V = OptimizeExpression(I, Ops)) {
|
|
if (V == I)
|
|
// Self-referential expression in unreachable code.
|
|
return;
|
|
// This expression tree simplified to something that isn't a tree,
|
|
// eliminate it.
|
|
LLVM_DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
|
|
I->replaceAllUsesWith(V);
|
|
if (Instruction *VI = dyn_cast<Instruction>(V))
|
|
if (I->getDebugLoc())
|
|
VI->setDebugLoc(I->getDebugLoc());
|
|
RedoInsts.insert(I);
|
|
++NumAnnihil;
|
|
return;
|
|
}
|
|
|
|
// We want to sink immediates as deeply as possible except in the case where
|
|
// this is a multiply tree used only by an add, and the immediate is a -1.
|
|
// In this case we reassociate to put the negation on the outside so that we
|
|
// can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
|
|
if (I->hasOneUse()) {
|
|
if (I->getOpcode() == Instruction::Mul &&
|
|
cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
|
|
isa<ConstantInt>(Ops.back().Op) &&
|
|
cast<ConstantInt>(Ops.back().Op)->isMinusOne()) {
|
|
ValueEntry Tmp = Ops.pop_back_val();
|
|
Ops.insert(Ops.begin(), Tmp);
|
|
} else if (I->getOpcode() == Instruction::FMul &&
|
|
cast<Instruction>(I->user_back())->getOpcode() ==
|
|
Instruction::FAdd &&
|
|
isa<ConstantFP>(Ops.back().Op) &&
|
|
cast<ConstantFP>(Ops.back().Op)->isExactlyValue(-1.0)) {
|
|
ValueEntry Tmp = Ops.pop_back_val();
|
|
Ops.insert(Ops.begin(), Tmp);
|
|
}
|
|
}
|
|
|
|
LLVM_DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
|
|
|
|
if (Ops.size() == 1) {
|
|
if (Ops[0].Op == I)
|
|
// Self-referential expression in unreachable code.
|
|
return;
|
|
|
|
// This expression tree simplified to something that isn't a tree,
|
|
// eliminate it.
|
|
I->replaceAllUsesWith(Ops[0].Op);
|
|
if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
|
|
OI->setDebugLoc(I->getDebugLoc());
|
|
RedoInsts.insert(I);
|
|
return;
|
|
}
|
|
|
|
if (Ops.size() > 2 && Ops.size() <= GlobalReassociateLimit) {
|
|
// Find the pair with the highest count in the pairmap and move it to the
|
|
// back of the list so that it can later be CSE'd.
|
|
// example:
|
|
// a*b*c*d*e
|
|
// if c*e is the most "popular" pair, we can express this as
|
|
// (((c*e)*d)*b)*a
|
|
unsigned Max = 1;
|
|
unsigned BestRank = 0;
|
|
std::pair<unsigned, unsigned> BestPair;
|
|
unsigned Idx = I->getOpcode() - Instruction::BinaryOpsBegin;
|
|
for (unsigned i = 0; i < Ops.size() - 1; ++i)
|
|
for (unsigned j = i + 1; j < Ops.size(); ++j) {
|
|
unsigned Score = 0;
|
|
Value *Op0 = Ops[i].Op;
|
|
Value *Op1 = Ops[j].Op;
|
|
if (std::less<Value *>()(Op1, Op0))
|
|
std::swap(Op0, Op1);
|
|
auto it = PairMap[Idx].find({Op0, Op1});
|
|
if (it != PairMap[Idx].end()) {
|
|
// Functions like BreakUpSubtract() can erase the Values we're using
|
|
// as keys and create new Values after we built the PairMap. There's a
|
|
// small chance that the new nodes can have the same address as
|
|
// something already in the table. We shouldn't accumulate the stored
|
|
// score in that case as it refers to the wrong Value.
|
|
if (it->second.isValid())
|
|
Score += it->second.Score;
|
|
}
|
|
|
|
unsigned MaxRank = std::max(Ops[i].Rank, Ops[j].Rank);
|
|
if (Score > Max || (Score == Max && MaxRank < BestRank)) {
|
|
BestPair = {i, j};
|
|
Max = Score;
|
|
BestRank = MaxRank;
|
|
}
|
|
}
|
|
if (Max > 1) {
|
|
auto Op0 = Ops[BestPair.first];
|
|
auto Op1 = Ops[BestPair.second];
|
|
Ops.erase(&Ops[BestPair.second]);
|
|
Ops.erase(&Ops[BestPair.first]);
|
|
Ops.push_back(Op0);
|
|
Ops.push_back(Op1);
|
|
}
|
|
}
|
|
// Now that we ordered and optimized the expressions, splat them back into
|
|
// the expression tree, removing any unneeded nodes.
|
|
RewriteExprTree(I, Ops);
|
|
}
|
|
|
|
void
|
|
ReassociatePass::BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT) {
|
|
// Make a "pairmap" of how often each operand pair occurs.
|
|
for (BasicBlock *BI : RPOT) {
|
|
for (Instruction &I : *BI) {
|
|
if (!I.isAssociative())
|
|
continue;
|
|
|
|
// Ignore nodes that aren't at the root of trees.
|
|
if (I.hasOneUse() && I.user_back()->getOpcode() == I.getOpcode())
|
|
continue;
|
|
|
|
// Collect all operands in a single reassociable expression.
|
|
// Since Reassociate has already been run once, we can assume things
|
|
// are already canonical according to Reassociation's regime.
|
|
SmallVector<Value *, 8> Worklist = { I.getOperand(0), I.getOperand(1) };
|
|
SmallVector<Value *, 8> Ops;
|
|
while (!Worklist.empty() && Ops.size() <= GlobalReassociateLimit) {
|
|
Value *Op = Worklist.pop_back_val();
|
|
Instruction *OpI = dyn_cast<Instruction>(Op);
|
|
if (!OpI || OpI->getOpcode() != I.getOpcode() || !OpI->hasOneUse()) {
|
|
Ops.push_back(Op);
|
|
continue;
|
|
}
|
|
// Be paranoid about self-referencing expressions in unreachable code.
|
|
if (OpI->getOperand(0) != OpI)
|
|
Worklist.push_back(OpI->getOperand(0));
|
|
if (OpI->getOperand(1) != OpI)
|
|
Worklist.push_back(OpI->getOperand(1));
|
|
}
|
|
// Skip extremely long expressions.
|
|
if (Ops.size() > GlobalReassociateLimit)
|
|
continue;
|
|
|
|
// Add all pairwise combinations of operands to the pair map.
|
|
unsigned BinaryIdx = I.getOpcode() - Instruction::BinaryOpsBegin;
|
|
SmallSet<std::pair<Value *, Value*>, 32> Visited;
|
|
for (unsigned i = 0; i < Ops.size() - 1; ++i) {
|
|
for (unsigned j = i + 1; j < Ops.size(); ++j) {
|
|
// Canonicalize operand orderings.
|
|
Value *Op0 = Ops[i];
|
|
Value *Op1 = Ops[j];
|
|
if (std::less<Value *>()(Op1, Op0))
|
|
std::swap(Op0, Op1);
|
|
if (!Visited.insert({Op0, Op1}).second)
|
|
continue;
|
|
auto res = PairMap[BinaryIdx].insert({{Op0, Op1}, {Op0, Op1, 1}});
|
|
if (!res.second) {
|
|
// If either key value has been erased then we've got the same
|
|
// address by coincidence. That can't happen here because nothing is
|
|
// erasing values but it can happen by the time we're querying the
|
|
// map.
|
|
assert(res.first->second.isValid() && "WeakVH invalidated");
|
|
++res.first->second.Score;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
PreservedAnalyses ReassociatePass::run(Function &F, FunctionAnalysisManager &) {
|
|
// Get the functions basic blocks in Reverse Post Order. This order is used by
|
|
// BuildRankMap to pre calculate ranks correctly. It also excludes dead basic
|
|
// blocks (it has been seen that the analysis in this pass could hang when
|
|
// analysing dead basic blocks).
|
|
ReversePostOrderTraversal<Function *> RPOT(&F);
|
|
|
|
// Calculate the rank map for F.
|
|
BuildRankMap(F, RPOT);
|
|
|
|
// Build the pair map before running reassociate.
|
|
// Technically this would be more accurate if we did it after one round
|
|
// of reassociation, but in practice it doesn't seem to help much on
|
|
// real-world code, so don't waste the compile time running reassociate
|
|
// twice.
|
|
// If a user wants, they could expicitly run reassociate twice in their
|
|
// pass pipeline for further potential gains.
|
|
// It might also be possible to update the pair map during runtime, but the
|
|
// overhead of that may be large if there's many reassociable chains.
|
|
BuildPairMap(RPOT);
|
|
|
|
MadeChange = false;
|
|
|
|
// Traverse the same blocks that were analysed by BuildRankMap.
|
|
for (BasicBlock *BI : RPOT) {
|
|
assert(RankMap.count(&*BI) && "BB should be ranked.");
|
|
// Optimize every instruction in the basic block.
|
|
for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;)
|
|
if (isInstructionTriviallyDead(&*II)) {
|
|
EraseInst(&*II++);
|
|
} else {
|
|
OptimizeInst(&*II);
|
|
assert(II->getParent() == &*BI && "Moved to a different block!");
|
|
++II;
|
|
}
|
|
|
|
// Make a copy of all the instructions to be redone so we can remove dead
|
|
// instructions.
|
|
OrderedSet ToRedo(RedoInsts);
|
|
// Iterate over all instructions to be reevaluated and remove trivially dead
|
|
// instructions. If any operand of the trivially dead instruction becomes
|
|
// dead mark it for deletion as well. Continue this process until all
|
|
// trivially dead instructions have been removed.
|
|
while (!ToRedo.empty()) {
|
|
Instruction *I = ToRedo.pop_back_val();
|
|
if (isInstructionTriviallyDead(I)) {
|
|
RecursivelyEraseDeadInsts(I, ToRedo);
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
|
|
// Now that we have removed dead instructions, we can reoptimize the
|
|
// remaining instructions.
|
|
while (!RedoInsts.empty()) {
|
|
Instruction *I = RedoInsts.front();
|
|
RedoInsts.erase(RedoInsts.begin());
|
|
if (isInstructionTriviallyDead(I))
|
|
EraseInst(I);
|
|
else
|
|
OptimizeInst(I);
|
|
}
|
|
}
|
|
|
|
// We are done with the rank map and pair map.
|
|
RankMap.clear();
|
|
ValueRankMap.clear();
|
|
for (auto &Entry : PairMap)
|
|
Entry.clear();
|
|
|
|
if (MadeChange) {
|
|
PreservedAnalyses PA;
|
|
PA.preserveSet<CFGAnalyses>();
|
|
return PA;
|
|
}
|
|
|
|
return PreservedAnalyses::all();
|
|
}
|
|
|
|
namespace {
|
|
|
|
class ReassociateLegacyPass : public FunctionPass {
|
|
ReassociatePass Impl;
|
|
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid
|
|
|
|
ReassociateLegacyPass() : FunctionPass(ID) {
|
|
initializeReassociateLegacyPassPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnFunction(Function &F) override {
|
|
if (skipFunction(F))
|
|
return false;
|
|
|
|
FunctionAnalysisManager DummyFAM;
|
|
auto PA = Impl.run(F, DummyFAM);
|
|
return !PA.areAllPreserved();
|
|
}
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.setPreservesCFG();
|
|
AU.addPreserved<AAResultsWrapperPass>();
|
|
AU.addPreserved<BasicAAWrapperPass>();
|
|
AU.addPreserved<GlobalsAAWrapperPass>();
|
|
}
|
|
};
|
|
|
|
} // end anonymous namespace
|
|
|
|
char ReassociateLegacyPass::ID = 0;
|
|
|
|
INITIALIZE_PASS(ReassociateLegacyPass, "reassociate",
|
|
"Reassociate expressions", false, false)
|
|
|
|
// Public interface to the Reassociate pass
|
|
FunctionPass *llvm::createReassociatePass() {
|
|
return new ReassociateLegacyPass();
|
|
}
|